DETERMINATION OF SOLUTE DESCRIPTORS FOR ILLICIT DRUGS USING GAS

CHROMATOGRAPHIC RETENTION DATA AND ABRAHAM SOLVATION MODEL

Yannick K. Mitheo, B.S

Thesis Prepared for the Degree of

MASTER OF SCIENCE

UNIVERSITY OF NORTH TEXAS

August 2015

Committee members: Teresa D. Golden, Major professor

William E. Acree, Jr., Committee Member and Chair of the Department of Chemistry Sushama A. Dandekar, Committee member

Mark Wardell, Dean of The Robert B. Toulouse School of graduate studies

Mitheo, Yannick K. Determination of solute descriptors for illicit drugs using gas

chromatographic retention data and Abraham solvation model. Master of Science (Analytical

Chemistry), August 2015, 88 pp., 36 tables, 14 figures, references, 62 titles.

In this experiment, more than one hundred volatile organic compounds were analyzed

with the gas chromatograph. Six capillary columns ZB wax plus, ZB 35, TR1MS, TR5, TG5MS

and TG1301MS with different polarities have been used for separation of compounds and illicit

drugs. The Abraham solvation model has five solute descriptors. The solute descriptors are E, S,

A, B, L (or V). Based on the six stationary phases, six equations were constructed as a training

set for each of the six columns. The six equations served to calculate the solute descriptors for a

set of illicit drugs. Drugs studied are nicotine (S= 0.870, A= 0.000, B= 1.073), oxycodone(S=

2.564. A= 0.286, B= 1.706), methamphetamine (S= 0.297, A= 1.570, B= 1.009), heroin

(S=2.224, A= 0.000, B= 2.136) and ketamine (S= 1.005, A= 0.000, B= 1.126). The solute

property of Abraham solvation model is represented as a logarithm of retention time, thus the

logarithm of experimental and calculated retention times is compared.

ii

Copyright 2015

by

Yannick K. Mitheo

iii

ACKNOWLEDGEMENTS

I am very thankful and glad to have Dr. Teresa D. Golden as my mentor and advisor.

There are no better or proper words to express my deep, sincere gratitude and respect for my

research advisor than saying thank you. She has encouraged, supported and provided me with

every need possible in order to do my research. I am happy and humble for the opportunity she

offered me to work with her and the rest of the group to pursuit my future and become a better

learner. My sincere thank goes also to my committee members, Dr. William Acree and Dr.

Shushama Dandekar. Dr. Acree did provide some of the sample used for my thesis; with his

expertise, I was able to understand the chemistry behind this project.

I would like to thank Syeda Sabrina for training me on how to use the gas chromatograph

and Michel Stovall for her encouragement on how to be an independent person. I would like to

thank Dr. Golden research group members, Michael Kahl, Dylan Harbour, Casey Thurber, Ryan

Daugherty, Dr. Jeerapang Tientong, Dr. Heidi Conrad, Viviane Huynh, Teresa Allen, Stephen

Sanders, Ting Zhou, and Johnathan Bishop for the great time we spent together and for their

support. I appreciate the support and help from Benjamin Starr, Dylan Harbour and Timothy

Stephens who helped me throughout the whole process. I also wanted to thank the department of

chemistry at the University of North Texas for their financial assistance that motivated me to

work hard.

I want to take this opportunity to thank my family, my parents, my cousins, nieces,

nephews, uncles and closest friends for their encouragements, support, love and prayers through

the ups and downs. I want to thank my wife Dr. Chantal Tshikaya and her family for their

support, motivation and love.

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TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS ........................................................................................................... iii LIST OF TABLES ......................................................................................................................... vi LIST OF FIGURES ..................................................................................................................... viii CHAPTER 1 DESCRIBING ABRAHAM SOLVATION PARAMETER MODEL AND GAS CHROMATOGRAPHY ................................................................................................................. 1

1.1 Introduction ............................................................................................................. 1

1.2 Abraham Solvation Parameter Model ..................................................................... 5

1.2.1 E: Excess Molar refractivity ....................................................................... 5

1.2.2 S: Dipolarity/Polarizability ......................................................................... 6

1.2.3 A: Solute’s Hydrogen Bond Acidity and B: Solute Hydrogen Bond Basicity ................................................................................................................... 6

1.2.4 V: McGowan Volume ................................................................................. 8

1.2.5 L: Ostwald Solubility .................................................................................. 8

1.2.6 Process Coefficients .................................................................................... 8

1.3 Gas Chromatography ............................................................................................ 10

1.3.1 Beginning of Gas Chromatography (GC) ................................................. 10

1.3.2 Instrumentation of Gas Chromatography.................................................. 10

1.3.3 Advantage and Disadvantage of Gas Chromatography ............................ 11

1.3.4 Column Oven ............................................................................................ 12

1.3.5 Inlet System .............................................................................................. 15

1.3.5.1 Split/Splitless .............................................................................. 15

1.3.5.2 On-column .................................................................................. 16

1.3.6 Type of Analyte ........................................................................................ 16

1.3.7 Mobile Phase or Carrier Gas ..................................................................... 17

1.3.8 Detector ..................................................................................................... 17

1.4 Summary ............................................................................................................... 19 CHAPTER 2 RESEARCH PROCEDURE ................................................................................... 21

2.1 The Aim of this Research ..................................................................................... 21

2.2 Gas Chromatography Instrument .......................................................................... 21

v

2.3 Nature of Chemical Compounds ........................................................................... 23

2.4 Statistical Analysis ................................................................................................ 34

2.5 Training Sets ......................................................................................................... 35 CHAPTER 3 RESULT AND DISCUSSION ............................................................................... 36

3.1 Result from Each Column Used ........................................................................... 36

3.2 Discussion ............................................................................................................. 66

3.2.1 Active Compounds for Each Column ....................................................... 66

3.2.2 Data Interpretation .................................................................................... 71

3.2.3 Molecular Descriptors ............................................................................... 73

3.2.3.1 Nicotine ...................................................................................... 75

3.2.3.2 Oxycodone ................................................................................. 76

3.2.3.3 Methamphetamine ...................................................................... 77

3.2.3.4 Heroin ......................................................................................... 79

3.2.3.5 Ketamine .................................................................................... 80

3.3 Conclusion ............................................................................................................ 82 REFERENCES ............................................................................................................................. 84

vi

LIST OF TABLES

Page

Table 1.1 Summation of the Abraham solvation parameter model. ............................................... 9

Table 1.2. GC column packed vs capillary. .................................................................................. 14

Table 1.3. Available recommended stationary phases for different columns. .............................. 14

Table 1.4. Stationary phase interactions. ...................................................................................... 15

Table 1.5. Summary of common gas chromatography detector ................................................... 18

Table 2.1. Summary of all 6 columns stationary phase used in this experiment. ......................... 22

Table 2.2. Summary of method development ............................................................................... 23

Table 2.3 .Structure of Compounds and their boiling point ......................................................... 23

Table 2.4. Chemical and physical properties of drugs to be studied ............................................ 32

Table 3.1. Retention time (min) for column ZB Wax plus max temperature 250 °C (polyethylene glycol) column .............................................................................................................................. 36

Table 3.2. Retention time (min) for ZB –35 (35% Phenyl 65% dimethyl polysiloxane) columns....................................................................................................................................................... 38

Table 3.3. Retention time for TR 1 MS (100% dimethyl polysiloxane) column.......................... 41

Table 3.4. Retention time for TR 5(5 % phenyl methyl polysiloxane) column ............................ 43

Table 3.5. Retention time for TG 5- MS (5% diphenyl 95% dimethyl polysiloxane) column ..... 45

Table 3.6. Retention time (min) for TG 1301 MS (6% cyanopropylphenyl 94% dimethyl polysiloxane) column .................................................................................................................... 48

Table 3.7. Experimental gas-to-liquid partition coefficient data (E, S, A, B, and L) from the literature [50, 52-53]. .................................................................................................................... 50

Table 3.8. Experimental LogtR and LogtR calculated for column ZB wax plus ........................... 55

Table 3.9. Experimental LogtR and LogtR calculated for column ZB 35 ..................................... 56

Table 3.10. Experimental LogtR and LogtR calculated for column TR-1MS ............................... 57

Table 3.11. Experimental LogtR and LogtR calculated for column TR-5 ..................................... 59

Table 3.12. Experimental LogtR and LogtR calculated for column TG-5MS ............................... 60

vii

Table 3.13. Experimental LogtR and LogtR calculated for column TG-1301MS ......................... 61

Table 3.14. Retention time (min) of illicit drugs .......................................................................... 73

Table 3.15. Process coefficients for GC stationary phases ........................................................... 74

Table 3.16. Observed and calculated retention data for nicotine .................................................. 75

Table 3.17. Predicted solute descriptors for nicotine .................................................................... 75

Table 3.18. Observed and calculated retention data for oxycodone ............................................. 76

Table 3.19. Predicted solute descriptors for oxycodone ............................................................... 76

Table 3.20. Observed and calculated retention data for methamphetamine ................................. 77

Table 3.21. Predicted solute descriptors for methamphetamine ................................................... 77

Table 3.22. Observed and calculated retention data for heroin .................................................... 79

Table 3.23. Predicted solute descriptors for heroin ...................................................................... 79

Table 3.24. Observed and calculated retention data for ketamine ................................................ 80

Table 3.25. Predicted solute descriptors for Ketamine ................................................................. 81

Table 3.26Summary of predicted solute descriptors for nicotine, oxycodone, methamphetamine, heroin and ketamine ...................................................................................................................... 81

viii

LIST OF FIGURES

Page

Figure 1.1. Hydrogen-bond complexation reaction. Adapted from ref. 41 ..................................... 7

Figure 1.2. Schematic diagram of the components of a typical gas chromatograph. Adapted from http://en.wikipedia.org/wiki/gas_chromatography ....................................................................... 11

Figure 1.3. Picture of GC column oven and column from our la.b .............................................. 13

Figure 1.4. Column efficiency. clu-in.org/characterization/technologies/images/theoreticalz.gif 13

Figure 1.5. Split/splitless injector. ................................................................................................ 16

Figure 1.6. Flame ionization detector. .......................................................................................... 18

Figure 3.1. Correlation of LogtR (calculated) and LogtR (experimentally) observed for the six columns. ........................................................................................................................................ 65

Figure 3.2. Correlation of LogtR (calculated) and LogtR (experimentally) observed for the six columns ZB wax plus (a), ZB 35(b), TR- 1MS(c), TR-5(d), TG-5MS (e), TG1301 MS (f) for just active compounds.......................................................................................................................... 69

Figure 3.3. Structure of nicotine ................................................................................................... 76

Figure 3.4. Structure of oxycodone............................................................................................... 77

Figure 3.5. Structure of methamphetamine................................................................................... 79

Figure 3.6. Structure of heroin (left) and morphine(right) ............................................................ 80

Figure 3.7. Structure of ketamine ................................................................................................. 81

1

CHAPTER 1

DESCRIBING ABRAHAM SOLVATION PARAMETER MODEL AND GAS

CHROMATOGRAPHY

1.1 Introduction

Drug permeability across membranes is predicted by partition coefficients between an

aqueous or a gas phase and lipid phase. To better predict the effect of various functional groups

on partitioning, similar drug like molecules need to be studied.

The Abraham solvation model is used to predict the adsorption, distribution, metabolism,

elimination and toxicity (ADMET) properties of the drug molecules. It is a good approach for

studying and predicting biological activities and partition co-efficient. The introduction of early

ADME is important because it decreased the proportion of compounds failing in clinical trials.

The main goal of preclinical ADME is to remove weak drug candidates in the early stages of

drug development and allow the resources to be used on potential drug candidates.

Drug candidate’s ADMET (Adsorption, distribution, metabolism, elimination and

toxicity) properties of drugs discovery can be predicted computationally or experimentally. Only

20% of developed drug candidates proceed to clinical trial stage testing, and among those

compounds that enter clinical development less than 10% receive government approval. Drugs

failures occur because of poor bioavailability, poor solubility, toxicity concerns, drug-drug

interactions, degradation and poor shelf –life stability, and unfavorable pharmacokinetic

properties [1-3].

In general, most newly discovered drugs have higher molecular weights and have more

complicated molecular structures than previously discovered drugs; this explain the reasons why

most drug candidates fail in the early development stage. Drug permeability across membranes is

2

predicted by partition coefficients between an aqueous or a gas phase and lipid phase [4]. To

better predict the effect of various functional groups on partitioning, similar drug like molecules

need to be studied. Gas chromatography method is ideal for studying a large set of compounds.

Gas chromatography is one of the techniques to consider for studying the distribution of

drug compounds between different organic phases. The retention times obtained from the GC are

used to model biological activities that involve the transfer of a drug molecule from gas phase to

the biological phase. From the retention time; the solute descriptor are calculated, then the

solutes descriptors are correlated to the biological routes [5].

In order for drug to penetrate the central nervous system (CNS); it must cross through

blood brain barrier (BBB). The Abraham solvation model is used to predict the ADMET

properties of the drug molecules.

The Abraham solvation model is two linear free energy relationships (LFER) where one

equation described transfer process of the drug between two condenses phases.

SP = c+eE +sS +aA+ bB+vV

(1)

and the second describe gas to condense phase transfer

SP = c+eE +sS+ aA +bB +lL (2)

The solute property (SP) is the dependent variable. The SP represents the properties of a

series of analytes in a fixed phase. The independent known solutes descriptors (E, S, A, B, L, V)

are solute properties, they reflect the ability of the solute-solvent interaction. The process

coefficients or regression coefficients c, e, s, a, b, l, v describe the solvation properties which can

be obtained through multiple linear regression analysis (MLRA) [6]. ). c is a regression constant,

a and b are measure of solvent’s base properties and acid properties; e is the measure of solvent

dispersion interaction; s is the ability of the solvent phase to go through dipole –dipole induce

interaction with solute; l and v measure of size needed to form solvent cavity and dispersion

3

forces for a gas. The E is the excess molar refraction [( cm3mol-1/10]; S is solute

dipolarity/polarizability. The A and B are the effective hydrogen bond acidity and hydrogen

bond basicity, The V is the McGowan characteristic volume [(cm3mol-1)/100]. V can always be

calculated from the solute molecular formula, or known atomic size and number of chemical

bonds in the molecule. L is the logarithm of the solute gas phase dimensionless Ostwald partition

coefficient into hexadecane at 298 K. The V and L descriptors both measure size and are viewed

as measure of the solvent cavity term that will accommodate the dissolved solute.

There are more than 4000 organic, organometallic and inorganic solute descriptors

available or published. A large list of solute descriptors is available in one of the published

review articles [7], and in several other published papers [8-9]. Solute descriptors can be

obtained through regression analysis using different types of experimental data, gas to-solvent

partitions, solubility data and chromatographic retention data. The A, B and S descriptors need to

be determined experimentally. Once the retention time of any solute is obtained, it can be used to

calculate the natural log of retention time to solve equations (1) or (2). The process coefficients

can then be determined through multiple linear regression analysis of experimental logarithm of

retention time depending on the column used [10-12].

The use of molecular descriptors in the Abraham solvation model become very helpful to

understand which barriers the drug can cross and also the descriptors provide some information

about the molecule’s acidity, basicity and polarity. The Abraham solvation model can be applied

to both chemical and biological process (e.g. blood brain partition [13], human and rat intestinal

absorption [14], solubility [15-16]). The Abraham solvation model gives us some indication of

the solute properties in terms of the molecular solute descriptors. The literature search shows that

either the gas chromatography or high pressure liquid chromatography can be used for separation

4

of compounds depending on the goal of the project. For partitioning of a solute between two

condense phases, a high pressure liquid gas chromatography is preferred while for partitioning of

a solute from a gas to a condensed phase gas chromatography is needed. From the retention data,

the gas-liquid partition coefficient and other thermodynamic properties of mixing can be easily

created. Using the thermodynamic properties and appropriate models allows understanding of the

intermolecular interactions responsible for the solvation in the stationary phase [17-19]. Now, the

solvation parameter model makes a valuable tool for obtaining quantitative structure- property

relationship for biomedical, chemical and environmental processes. The model correlates a free

energy related property of a system to a six free energy descriptors describing the molecular

properties. The main goal is to create a suitable quantitative structure property relationship

(QSPR) to enable the prediction of further system properties for compounds lacking

experimental values. In QSPR studied, two approaches are used; the first is based on theoretical

descriptors. All needed parameters for prediction can be calculated simply from the three

dimensional representation of the molecular structure of each of the solutes of the mixtures, as

well as mixtures of chemically diverse compounds [20-21]. The disadvantage of the approach is

that the particular descriptors may be challenging to understand and the model may lack

chemical meaning. The second approach on review papers is based on descriptors determined

using the experimental technique such as gas chromatography. Abraham and co- workers have

published several papers and reviews showing the correlation of different models system for the

prediction of solute descriptors and the interpretation of data using chromatography technique for

separation of mixture[ 22-25]. Taft and Kamlet have established in the 1980, the simple concept

of linear solvation energy relationships (LERs). They have shown for several chemical systems

that some property which linearly correlated to a either a free energy of reaction, or a free energy

5

of transfer, or a activation energy can be correlated with several molecular property of the

solvents or solutes involved[26-30]. Chromatographic retention and logarithmic partition

coefficients ( LogKL) are linear free energy parameters, thus one can correlate these data with the

molecular properties of the solutes using the LSER model [31-34]

In the experiment, we are developing an Abraham solvation model correlation equation

that can predict and provide molecular descriptors for illicit drugs. More than one hundred

known compounds have been collected from published literature with known descriptors [35-

38]. Out of the five descriptors in equation (1) and (2), E and L or V descriptors can be found in

the literature for a known target drug compound. To calculate the other three descriptors(S, A,

B), equations (1) and (2) can be assigned the log of retention time (LogtR) with the calculated

process coefficients, thus the unknown descriptors can be predicted. Before obtaining the process

coefficients, the retention time of different compounds are needed from the gas chromatography

experiment. The prediction values of target drug compound can be achieved through multiple

linear regression analysis. The advantage of using the Abraham solvation model resides in the

newly developed column equation. Once retention times of unknown illicit drugs or compounds

are determined, it is a matter of plugging them in the developed stationary equation to get the

molecular descriptors. In order to use the Abraham model to predict the ADMET properties, one

must have a prior knowledge of the desired compound’s solute descriptors.

1.2 Abraham Solvation Parameter Model

1.2.1 E: Excess Molar refractivity

Solute molar refractivity, E, is the difference between the molar refractivity and the

alkane molar refractivity with the same McGowan volume V. E expresses the ability of the

polarizable electrons in the molecule to be involved in the solute-solvent interaction.

6

E = MRx (observed) – MRx (alkane of same Vx) [39]

(3)

Where E unit is in cm3mol-1/10. E can be calculated from the molecular structure of the

compound. The McGowan volume in the molar refraction, MRx can be calculated as

MRx = V*[(η2-1)/ (η2+2)]

(4)

Where V in equation 4 is the McGowan volume (unit is (cm3/mol)/10), and η is the pure

liquid solute refractive index at 25° C.

1.2.2 S: Dipolarity/Polarizability

S is the solute dipolarity or polarizability. It represents the tendency of a solute to

participate in dipole-dipole and induce dipole-dipole interactions. The S represents or reflects the

interactions that involve both induced and stable polarity of a solute. A large mass of data from

gas liquid chromatography (GLC) can determine the polarity.

1.2.3 A: Solute’s Hydrogen Bond Acidity and B: Solute Hydrogen Bond Basicity

A is the solute effective or summation hydrogen-bond acidity. This descriptor was

originally obtained from hydrogen complexation constants for mono –acid. Now, it’s obtained by

chromatographic or partition measurements. B is the effective or summation hydrogen-bond

basicity. For mono-bases, this descriptor was obtained from hydrogen complexation constants,

now poly bases can be found by partition measurements [40]. Both solute hydrogen bond

acidity and basicity descriptors describe the hydrogen donor and acceptor solute ability. The

Hydrogen bond acidity and basicity were developed by Abraham model solvation using the

equilibrium constant for the 1:1 reaction in carbon tetrachloride, CCl4 at 298 K. When carbon

tetrachloride, acid and base are present in a solution at low concentration, both will undergo

8

1.2.4 V: McGowan Volume

The McGowan volume is calculated from the atom and the numbers of bonds in the

solute molecule in partition system with two condense phases. All type of bonds is treated

equally in the solute, whether it is a single bond, double or triple bond. The number of bond can

be solve by this equation

B = N-1+ R (7)

Here B is the total number of bonds, N is the total number of atoms and R is the total

number of ring structures. V is related to the size of the molecule as well as the size of the

solvent cavity. The McGowan volume can be calculated as follow

V = [∑atom contributions – (6.56*B)]/100 (8)

1.2.5 L: Ostwald Solubility

The L is defined as gas-to-hexadecane partition coefficient at 25◦ C. The Ostwald

solubility can be measured experimentally from solute’s retention volume by gas liquid

chromatography. It does include the cavity effect and the London dispersion effect of process.

The process can be follow as

Solute (gas phase) ⇌ solute (hexadecane). (9)

1.2.6 Process Coefficients

The process coefficients shown on equation (1) and equation (2) reflect particular solute

–solvent interactions that correspond to chemical properties of the solvent phase. Process

coefficient e, is the measure of solvent dispersion interactions. It describes how the solvent or

phase interacts with the solute through π and n-electron pairs. We anticipate e to be positive, but

an electronegative atom in phase might change it to negative. s is the ability of the solvent phase

to go through dipole –dipole induce interactions with a solute. When s is positive, the molecule

polarity increase and it will prefer the condense phase. The a process coefficient reflects the

7

acid-base interactions. An illustration of hydrogen-bond complexation reactions is shown in

Figure 1.1[41]

Figure 1.1. Hydrogen-bond complexation reaction. Adapted from ref. 41

H-A is the acidic solute, the reference base solvent is CCl4 and the hydrogen bond

complex created is A-H-Cl-CCl3 . The solute descriptor A is created by applying the following

equation.

A = (LogKAH + 1.1) (5)

4.636 Log KA

H is the average hydrogen bond acidity for solutes in CCl4, 1.1 is the scale factor

that enable the A descriptor to go through the origin and 4.636 is the empirical factor that

maintains the acidity scale within a suitable range.

For the hydrogen bond basicity, the equation is represented by

B = (LogKBH + 1.1) (6)

4.636

LogKBH is the average hydrogen bond basicity for solute in CCl4, 1.1 is the scale factor

that enable the B descriptor to go through the origin and 4.636 is the empirical factor that so that

B= 1.00 for the hydrogen bond base hexamethylphosphortriamide which allows a suitable

working range for the B values. Solute can form more than one hydrogen bond with neighboring

molecules in bulk solvent, making the 1:1 complexation assumption inaccurate for certain

solutes [40].

9

complementary solvent hydrogen bond acidity. The b coefficient will be a measure of the solvent

phase hydrogen bond basicity. The l and v coefficients will include not only an endorgonic

cavity effect, but exergonic solute- solvent effects rising through solute polarizability. The c

coefficient is an independent constant generated by multi regression linear analysis (MLRA).

The c coefficient does contribute to the cavity formation and it is related to the nonpolar

interaction of the retention time [41-43]. This is direct for the gas-to-condensed phase partition

since there is no interaction in the gas phase. Equation (1) refers to difference between the

properties of two phases. Thus the positive values reflect that the solute will favor the condense

phase while the negative values will show a tendency to favor a gas phase. The Abraham

solvation model is a useful model that can predict and illustrate the solute-solvent interaction in a

system. Once the predicting equations are established in the system, one can just insert any new

solute or drug compound values for certain gas-phase to derive the new solute descriptor.

Table 1.1 Summation of the Abraham solvation parameter model. Solute descriptor Process Coefficient c: Linear regression constant E : Excess molar refractivity ( cm3/mol)/100

e: interaction of the solvent or phase with the solute through π and n-electron pairs

S: dipolarity/Polarizability s: ability of the solvent phase to go through dipole-dipole induce interaction with a solute

A: Hydrogen bond acidity a:measure of solvent's base properties B: Hydrogen bond basicity b: measure of solvent's acid properties L:Ostwald solubility l:measure of size needed to form solvent cavity and

dispersion forces for a gas V: McGowan volume(cm3/mol)/10 v: measure of size needed to form solvent cavity and

dispersion forces

10

1.3 Gas Chromatography

1.3.1 Beginning of Gas Chromatography (GC)

The discovery of the actual GC is generally attributed to A.T. James and Archer.J. P

Martin in their 1952 paper. They did report a separation of volatile fatty acids by partition

chromatography with nitrogen gas as a mobile phase and a stationary phase of silicone oil/stearic

acid supported on diatomaceous earth. But the origin of the GC lies in the 1941 publication in

which Martin, with R.L.M Synge, first described liquid phase partition chromatography [59-60].

The term chromatography was used by Mikhail Tswett based on the fact that it separated the

components of solution by color (liquid chromatography). The term Chroma means color,

graphein means writing.

1.3.2 Instrumentation of Gas Chromatography

Gas chromatography is an analytical technique that can be used to separate volatile

organic compounds based on partition or distribution of analyte between two phases in a system.

The two phases are the mobile and stationary phase. The GC contains partitioning between a

solid or liquid stationary phase kept on the column wall or on a solid sorbent and the gaseous

mobile phase. The organic volatile samples are separated due to differences in their partitioning

behavior between the mobile gas phase and the stationary phase in column. Since the partitioning

behavior depends on temperature, the central part of the GC which is the oven contains the

column. The distribution coefficient or partition coefficient measure the tendency of an analyte

to be attracted to the stationary phase

K = Cs/Cm (10)

K is the partition coefficient or distribution coefficient, Cs is the molar concentration of

analyte in the stationary phase, Cm is molar the concentration of analyte in mobile phase. Larger

11

K values lead to larger retention analyte time. K can be controlled by the stationary phase

chemical nature and the column temperature.

1.3.3 Advantage and Disadvantage of Gas Chromatography

The advantage of using gas chromatography is fast analysis, high efficiency which

implies high resolution. Gas chromatography is a non-destructive method, high quantitative

accuracy. GC is good for quantitative analysis of volatile compounds.

The disadvantage of gas chromatography resides in the limitation of sample to be

volatized. It’s not suitable for sample that degraded at high temperature (thermally labile).

The main components of the gas chromatography are the oven (where the column is and

where separation takes place), the detector, the inlet and other factors need to be considered for

better separation. A schematic representation of the gas chromatography in Figure 1.2a

Figure 1.2. Schematic diagram of the components of a typical gas chromatograph. Adapted from

http://en.wikipedia.org/wiki/gas_chromatography

12

The sample is introduced to the instrument through the inlet part (vaporized) with the

help of carrier gas or mobile phase (usually helium gas, nitrogen or argon), then the carrier gas is

forced through the stationary phase (column).The stationary phase needs to be something that

does not react with the mobile phase. Then the sample has a chance to interact with the stationary

phase as it moves past it. Because of the differences in rates, samples can be separated into their

components. Sample that interact greatly, appear to move more slowly, those that have weak

interaction appear to move more quickly. Then the detector records the signal which is called a

peak. The peak is proportional to the amount of analyte injected. Other factors that need to be

considered are the sample type, the column oven, type of detector, the injection system and

carrier gas.

1.3.4 Column Oven

The column oven is the central part of the gas chromatography, the separation of mixture

or components take place in the column. The oven temperature is programed at different rate

with isothermal set as chosen. The GC separation is based on temperature, the higher the

temperature, the faster the sample will elute. Higher temperature can lead to poor separation

because of less interaction between the solute and the stationary phase. The temperature can be

programmed or isothermally controlled. If a sample has a high boiling point (100 ◦C and above);

the temperature needs to be programmed, the separation required increasing the temperature

during the run. A good separation occurs when the temperature is ramped and increased at slow

rate. Isothermal temperature is advantages for optimal resolution.

13

Figure 1.3. Picture of GC column oven and column from our la.b

A measure of the separation column efficiency is the number of theoretical plates which

is defined by:

N = 16(tR/W)2 (11)

Where N is the number of theoretical plates, tR is the total retention time and W is width

of the peak at the base

Figure 1.4. Column efficiency. clu-in.org/characterization/technologies/images/theoreticalz.gif

Inject

Detec

Colu

Column

N =

14

The resolution of the peak is how well the peak are separated

R = 2(tR2- tR1)/ (W1 + W2) (12)

Where R is the resolution, tR1 and tR2 are the total retention times for component 1 and 2,

W1 and W2 are peak widths for substance 1 and 2 respectively.

There are two types of columns used for the GC, a capillary (mostly used) and the packed

column. Here is a table that distinguished both types of columns.

Table 1.2. GC column packed vs capillary. GC column packed vs capillary Packed columns Capillary columns Usually a glass or stainless steel coil Thin fused-silica filled with a packing coated material 0.5-3 m long typically 1-100m in length 5 mm internal diameter 0.1-1 mm internal diameter 6 mm outside diameter film thickness 0.1-0.5 µm

The factors that affect the column performance are the column diameter, column length,

and the chemical inside the stationary phase [61, 44-45]

Table 1.3. Available recommended stationary phases for different columns. Type of compounds Polarity of compound Preferred stationary phase Alcohols, Ketones, esters, carboxylic acid diols, amine

Polar compounds containing Cl, F, Br, O, P, N, S other than C and H atom

20% diphenyl/ 80% dimethyl siloxane, 6% cyanopropylphenyl/94% dimethylsiloxane, 35%diphenyl/65% dimethylsiloxane, 50% diphenyl/50% dimethyl siloxane, ethylene glycol, alkylene glycol

Alkanes Non Polar C and H atom only C-C bond

5% diphenyl/95% dimethylsiloxane, methyl silicone,50% n-octyl/50% methylsiloxane

Alkenes, Arenes, alkynes aromatic hydrocarbon bonds.

Polarizable C and H atom only, C=C or C=C

80%biscyanopropyl/20% cyapropylphenyl siloxane, 90%biscyanoprophyl/10% cyanopropylphenyl siloxane

15

Table 1.4. Stationary phase interactions. Functional group

Dispersion Dipole Hydrogen bonding

Methyl strong none none Phenyl strong none to weak weak Cyanopropyl strong very strong moderate Trifluoropropyl strong moderate weak PEG strong strong moderate

Table 1.4 shows the dispersion, dipole and hydrogen bonding of different functional

group for the stationary phase interactions [47].

1.3.5 Inlet System

The amount of analyte to be injected to the column must be controlled so that the inlet

system does not deliver a huge amount of sample to the column. The sample must be vaporized

prior to get into the column. The injector should not be too hot; otherwise the sample will be

decomposed. The set of temperature is 50 °C above the boiling of the highest boiling sample.

The peak shape will be poor if the temperature is too low. The inlet system has a microsyringe

through which the simple is introduce to the inlet port. The syringe must be a gas-tight type to

avoid loss of sample. Inside the inlet, there is an inlet liner that provides proper mixing of sample

vapor with carrier gas and prevents non-volatile material to get in contact with the column.

There are two types of injection system.

1 split/splitless

2 On column

1.3.5.1 Split/Splitless

In split/splitless mode the sample is injected after mixing with the carrier gas, then it

splits into two unequal portions. One part goes to the column; the other portion goes to waste.

The disadvantage of split mode is that the rest of sample that did not go to the column is wasted.

With the splitless option, the whole amount of sample is injected through the column. The

16

splitless mode is usually applied for trace analysis. The issue with splitless mode is that it puts

high solvent load on the column.

Figure 1.5. Split/splitless injector. 1.3.5.2 On-column

It’s a mode of injection that avoids the hot injection liner all together is suitable for

thermally unstable (labile) analyte or GC analyte with a boiling point differences that undergo

discrimination in flash vaporization. It is widely use in packed column. It’s the cold on-column

injector. On column injector, a tall, low thermal –mass extension is attached to the top of the

injector. It keeps the needle cool from the heat coming from the GC oven at the top of its

temperature program [46].

1.3.6 Type of Analyte

The sample to be analyzed must be volatile enough in order to go through the column

with the help of carrier gas such as helium or nitrogen. Derivatization of compounds can be done

for analyte that is not volatile enough before separation. Careful precaution needs to be taken

17

when running a mixture of volatile and non-volatile compounds to avoid the interference of non-

volatile to the compound of interest.

1.3.7 Mobile Phase or Carrier Gas

The role of the carrier gas is to help transport the analyte through the column.

The GC carrier gas needs to be inert with the analyte, dry and free of oxygen to prevent

column deterioration. The helium gas or nitrogen (carrier gas) needs to be pure (99.999% or

more), otherwise the quantitative analysis will be of noisy baseline, poor sensitivities.

Maintaining a constant flow is necessary to avoid change in the retention time.

1.3.8 Detector

There are several types of detector for different purposes. The universal detector used in

our GC is the flame ionization detector (FID). An FID normally uses hydrogen/air flame into

which the analyte is passed to oxidize organic molecules and produces electrically charged

particles (ions). The ions are collected and thus produce an electrical signal which is then

measured. The detector role is to produce an electrical response proportional to the sample

concentration. Flame ionization detectors are subjects to two broad trouble categories which are

contamination and electronics. Contamination is by far the most common problem. Everything

that passes through a FID is burned in the hydrogen flame. Large amounts of chlorinated

compound or carbon disulfide however are not burned as well as hydrocarbons. Carbon particle

tends to aggregate between the jet and the collector forming an electrical leakage path, and the

result is high, noisy baseline. Another type of problem is stationary phase bleed from the column

into the detector. To check the detector contamination, the GC power must be turn off and shut

off the combustion gas flow. The FID is a mass sensitive detector; it depends on the mass of

analyte entering the detector per unit time. The disadvantage of flame ionization detector is that

18

it destroys everything coming out of the column. The main part of the flame ionization detector

is the ion chamber which is made of stainless steel, including the gas inlet, flame nozzle, a pair

of electrodes and housing. The column flow rate has an impact on the detector’s response.

Current is detected when eluent burns and generates ions; there is a change between the jet and

the collector electrode. The current is amplified by the electrometer, producing a response. The

information can be recorder as peak area, retention time and peak height. The retention time is

the time taken for a particular compound to travel through the column to the detector.

Qualitative and Quantitative analysis can be observed through the computer program recorder

[48]

Figure 1.6. Flame ionization detector.

Table 1.5. Summary of common gas chromatography detector

Detector Type Detectability Selectivity Dynamic Range

Flame ionisation detector (FID) Mass flow 100 pg most organic

compounds/universal 107

Thermal conductivity (TCD) concentration 1 ng universal 107

Photo-ionization (PID) concentration 2pg Aliphatics, aromatics,ketones 107

Esters,aldehydes, amines,

heterocyclics, organosulfurs

Electron capture (ECD) concentration 50 fg Halides, nitrates,nitriles 105

anhydrides,

organometallics

19

Flame photometric (FPD) mass flow 100 pg sulfur, tin, boron, 103

phosphorus, arsenic, selenium, chromium Halides, nitrates,nitriles

anhydrides,

organometallics Nitrogen phosphorus

(NPD) mass flow 10 pg Nitrogen, phosphorus 106

The type of detector to use depends on the goals of the experiment and the type of analyte

to be studied. Each detector will give different type of selectivity. In our case we are using the

FID universal detector. Most of these detectors use helium or nitrogen as carrier gases. Most

detectors use hydrogen and air or make up gases and other may use hydrogen and air possibly

oxygen as support gases.

1.4 Summary

Gas chromatography is a method for separating substance in a mixture and measuring the

relative quantities of substance. The result in gas chromatography provides the peak area or peak

height and the retention time. In this experiment the retention time of different solutes are used in

the Abraham solvation model equation to predict solute descriptors. The experimental retention

time data can be applied through the Abraham solvation model to predict various and significant

chemical and biological properties of pharmaceutical importance. The retention time is a

reflection of the substance’s affinity for the stationary phase. The retention time can be used as

property to characterize the compound. We can rely on the retention time only when measuring

reference or sample under identical conditions and shorty after each other.

Once the drug’s descriptors are determined, they can be used to predict the partitioning

behavior of molecule through different biological barriers. In this experiment, the partitioning

coefficients are determined by measuring the retention time and using them in the appropriate

20

equation. The partitioning coefficient tells us whether or not the chemical will cross the

biological membranes. These partitioning coefficients also relate to the effects of solvent phase

on solute-solvent phase. Right now, we are adding more solutes to develop the equation for gas

chromatography stationary phase to predict solutes descriptors for illicit drugs from the GC

retention time and structural information.

21

CHAPTER 2

RESEARCH PROCEDURE

2.1 The Aim of this Research

The goal of this research is to experimentally determine solute descriptors for certain

drug compounds. First the gas chromatography is used to obtain the retention time of drug

compounds, then the chromatography data (retention time) is applied to calculate the molecular

descriptors with the use of Abraham solvation model equation (2). After obtaining the molecular

or solute descriptors, they are used to predict some chemical or biological properties as

mentioned in chapter one. More than one hundred compounds were used in this experiment. The

advantage of using the Abraham solvation model resides in the newly developed column

equation. Once the retention times of unknown illicit drugs or compounds are determined, it is a

matter of plugging them in the developed stationary equation to get the solute descriptors.

2.2 Gas Chromatography Instrument

In this study, a gas chromatograph with flame ionization detector (FID) (Thermo Fisher

Scientific, Model GC FOCUS) is used to obtain the retention times. Chromquest software was

used to analyze the data. The helium carrier gas flow rate was set to 1.5 ml/min.

Six different chromatographic columns were used for separations. Column TR-5, TR1-

MS, TG-1301MS, TG- 5MS all bought from Fisher Scientific, and column ZB-Wax, Zb-35

purchased from Zebron. All 6 columns had the same length (30m), same internal diameter

(0.32mm) and film thickness (.25µm). A summary of the columns stationary phase is shown in

Table 2.

Six different chromatographic columns were used for separations. Column TR-5, TR1-

MS, TG-1301MS, TG- 5MS all bought from Fisher Scientific, and column ZB-Wax, Zb-35

22

purchased from Zebron. All 6 columns had the same length (30m), same internal diameter

(0.32mm) and film thickness (.25µm). A summary of the columns stationary phase is shown in

Table 2.1.

Table 2.1. Summary of all 6 columns stationary phase used in this experiment. Column Stationary Phase Polarity Max.

Temp. Recommended

ZB-wax plus

Polyethylene glycol Polar 250 °C Glycols, aromatic isomers, esters, Alcohol ketones

ZB-35

35% phenyl 65% dimethyl polysiloxane

mid- polarity

340 °C Pharmaceutical steroids, semi volatile amines

TR 1MS 100% dimethyl polysiloxane

Non polar

360 °C Chlorinated and nitro aromatic compounds

TR 5 5% phenyl methyl

Low polarity

350 °C Alcohols, low pesticides, free fatty acids, aromatic flavors

TG5 MS 5% diphenyl 95% dimethyl polysiloxane

low- polarity

350 °C Semi volatile, phenol, amines

TG 1301MS

6% cyanopropyl phenyl 94% dimethyl polysiloxane

Mid polarity

280 °C Oxygenate residuals, solvent, alcohols, volatile organics

The chemical compounds and the illicit drugs were all dissolved in methanol,

dichloromethane, dimethylsulfoxide (DMSO) or acetonitrile to make solution for injection. Both

liquid and solid concentration is 1 mg/ml. Low boiling point compounds like ethanol, ethyl

acetate, methyl acetate, acetone, and butanone are diluted with dichloromethane or DMSO

because the methanol solvent peak can co-elutes with the peak of interest.

The run starts at initial oven low temperature of 50 degree Celsius, with a hold time of 2

minutes. Then the temperature is raised at the rate of 15◦C per minute with 5 minutes hold time

to the final temperature depending on the maximum temperature of the column inside the oven.

The maximum temperature of the oven on average is 260-330◦C, prep-run timeout is 10.00

minute and equilibrium time is 0.50 minute. The FID detector temperature is 200◦C. The inlet

temperature is 240◦C. The injection volume of sample is 1µl, but can vary depending on the peak

23

area of the sample. The split ration of the analyte can vary too. Methanol is used to wash the

needle for pre and post injection of the sample for three cycles. The needle itself is rinsed with

the sample three times before injection. Each sample was tested three times to reproduce

accurate and precise data. The column is conditioned twice in between each run to make sure

there is no carry over or no interference with the retention time of the desire sample. Below is a

summary of method development.

Table 2.2. Summary of method development Sample concentration 1 mg/ml Injection volume 1.0µl Split ratio 50:1 Split mode Split Column Dimension 30 m x 0.32 mmID x 0.25µm film thickness Carrier flow rate 1.5 ml/min Carrier gas Helium Initial oven temperature 50◦C ( hold for 2 min) Final oven temperature 330◦C ( depending on the column max temp(

hold for 5 min) Injector temperature 240◦C Pre run time 10 min Equilibrium time 0.5 min Ramp 15◦C/min Detector FID Detector temperature 200◦C Solvents Methanol, DCM. DMSO

2.3 Nature of Chemical Compounds

There are several type of compounds selected with a wide range of boiling point and size.

The compounds to be run need to have similar functional group with the drug sample.

Compounds need to be volatile in order to be run in the gas chromatograph.

Below is the list of more than one hundred compounds run in Table 2.2

Table 2.3 .Structure of Compounds and their boiling point

Solute Structure Boiling point(◦C)

24

1- Bromopropane CH3

Br

71

1,2- Dibromoethane Br

Br

131

1,2-Dichlorobenzene

180

1,2-Dimethylbenzene

144

1-Bromohexane

CH3 Br 158

1-Butanol CH3 OH

117.4

1-Chloronaphthalene

263

1-Nitronaphthalene

304

1-Nonene CH2

CH3

146

1-Octanol OH CH3

195

1-Octene CH2

CH3

121

2 Propanol CH3 CH3

OH

82

2-Acetylpyridine

189

2-Butanone

79.6

25

2-Butoxyethanol CH3 O

OH

171

2-Chlorobenzoic acid

285

2-Chlorophenol

175

2-Methyl -2-pentanol

121

2-Methyl-1-propanol

108

2-Methyl-2-propanol

OH

82

2-Naphthol

286

2-Octanol

195

2-Picoline

129

3-Amino-1-propanol

188

3-Nitrobenzoic acid

341

4-Chlorophenol

220

4-Methyl-2 pentanol

132

4-Nitrophenol

279

26

4-Nitrotoluene O2N

CH3

238

Acenaphthene

280

Acetamide

222

Acetanilide

304

Acetic Acid

118

Acetic anhydride

139

Acetone

56.5

Acetophenone CH3

O

202

Alpha pinene

155

Amyl acetate

148

Aniline

186

Aspirin

140

Benzene

80.1

27

Benzoic Acid

249

Benzonitrile

191

Benzophenone

305.4

Benzyl Alcohol OH

205

Benzyl bromide Br

198

Benzyl chloride Cl

179

Biphenyl

255

Bromobenzene Br

156

Butyric acid

163.5

Butyronitrile

N

CH3

117

Caffeine

178

Chloroacetic acid

189

Chlorobenzene Cl

132

28

Cyclohexane

80.7

Cyclohexanol

161

Diiodomethane

181

Diisopropylamine

84

Dimethyl carbonate

90

Ethanol

CH3 OH

78.5

Ethanolamine NH2

OH

170

Ethyl Acetate

77

Ethyl Acetoacetate

180.8

Ethyl benzoate

213

Ethyl decanoate

245

Ethyl benzene CH3

136

Ethylene glycol OH

OH

195

Formamide NH2

O

H 210

29

Formic acid OH

O

H 107.3

Imidazole NH

N 256

Indole NH

254

Iodobenzene I

189

Iso-pentyl acetate

287.6

Isoquinoline

242

L Menthol OHCH3

CH3

CH3

212

Lactic acid

122

Malonic acid

140

Mesitylene

164.7

Methyl Acetate

56.9

Methyl Benzoate

199.6

Methyl isobutyl ketone

115.9

Methyl-4-hydroxybenzoate

298.6

30

Morpholine

129

m-Toluic acid

263

N,N-Diethylaniline

217

N,N-Dimethylacetamide

165

N,N-Dimethylaniline

194

N,N-Dimethylformamide

153

Naphthalene

218

nitrobenzene

210.9

Nitromethane NO2CH3

100

Nonylamine CH3

NH2

201

N,propyl alcohol CH3

OH

97.2

o-anisaldehyde

238

o-cresol

191

Octanoic acid

237

31

Octylamine CH3

NH2

176

Pentan-1-ol CH3

OH

139

Phenanthrene

332

Phenol OH

181.7

Phenylacetic Acid

265.5

Piperazine NH

NH

146

Piperidine NH

106

Propanoic Acid

141

Propionitrile

97

Propylene Carbonate

240

Pyrazine N

N 115

Pyridine N

115.2

Pyrrole NH

129

32

Quinoline

237

Resorcinol

277

Tetrachloroethylene

121.1

Tetrahydrofuran

66

Toluene

CH3

110.6

Triethyl amine

89.7

Vanillin

285

Xanthene O

312

Illicit and prescription drugs to be studies are methamphetamine, oxycodone, nicotine,

heroin and ketamine. The drugs chemical formula and other information are listed below in

Table 2.3

Table 2.4. Chemical and physical properties of drugs to be studied Compound Chemical

Structure Molecular Formula

Molecular Weight (g/mol)

Boiling Point (ºC)

Methamphetamine

C10H15N 149.23 212

33

Oxycodone

C18H21NO4 315.36 501

Ketamine

C13H16ClNO 237.72 262

Heroin(diacetyl morphine)

C21H23NO5 369.41 273

Nicotine

C10H14N2 162.23 247

Chemical compounds in Table 2.2 have some similar functional groups to the drug

compounds in Table 2.3. HPLC grade (Spectrum chemical Mfg.Corp.), analytical grade

dichloromethane (Spectrum chemical Mfg.Corp.), DMSO, ACN are solvents used to dissolved

drug samples and compounds. Once the retention time of each compound is obtained, equation

(2) is used to solve Abraham solvation parameter model with the retention time of each

compound using the experimental gas-to liquid partition coefficients data( E,S,A,B,L,V) from

literature [49-52]. The software utilized to calculate the process coefficients by multiple linear

regression analysis (MLRA) is the statistical package for social science (SPSS). The SPSS is

software for managing data and calculate a wide variety of statistics. With the use of SPSS, the

processes coefficients are obtained, then the log of calculated retention time are found. Multiple

34

linear regression analysis is a technique that correlates two or more independent variable (x) and

a dependent variable(y) to produce equation coefficients. MLRA is used to construct linear free

energy relationships with the Abraham solvation parameter model. The method of MLRA can be

used with Microsoft excel or SPSS. In order to produce a good quality regression for five

variables, one needs to have at least thirty samples.

2.4 Statistical Analysis

The data analyses are examined with the use of SPSS software and Microsoft excel. First,

each compound is run three times, and then the average of the three run is obtained. Next the

standard deviation is calculated. Standard deviation shows how much variation or dispersion

from the average exists. A large standard deviation indicates that data points are spread out over

a large range of values, therefore poor relationships among data. A low standard deviation

indicates that data points tend to be very close to the mean, thus a good relationship among data.

A low standard deviation is preferable because it shows a good relationship among data. After

the standard deviation, the logs of experimental retention times are calculated. Once the

calculated log and experimental log of retention time are acquired, excel or origin program can

be used to graph the experiment log of retention time on x axis versus the calculated log of

retention time on y axis. The correlation coefficient, r reflects the linear relationship between the

two variables. A positive sign (+1) on the correlation coefficient indicates a positive or direct

correlation between two variables. A negative sign (-1) indicates an indirect correlation between

two variables. The correlation coefficient denoted by r2 or R2 is a measure of the strength of the

straight line or linear relationship between two variables.

35

2.5 Training Sets

Since there are five unknowns (E, S, A, B, L or V) to be solved in the Abraham solvation

model, there is a need of at least five equations to be established in order to determine the solute

descriptors of illicit drugs. The known process coefficients (e, s, a, b, l or v) are used through the

system equations to generate the solute descriptors or molecular descriptors. The process

coefficients for each column are calculated with the help of the SPSS software by multiple linear

regression analysis. The overall sums of squares are set at a minimum to fit the aimed cells of S,

A, and B in excel where A and B are set as unconstrained variable with a values of greater than

or equal to zero since acidity and basicity cannot be negative. The S is set as unrestrained

variable. The method used is the Microsoft excel solver that uses the generalized reduced

gradient (GRG2) algorithm for optimizing nonlinear problems. This algorithm was developed by

Leon Lasdon, of the University of Texas at Austin, and Allan Warren, of Cleveland State

University

36

CHAPTER 3

RESULT AND DISCUSSION

3.1 Result from Each Column Used

In this experiment, more than one hundred compounds were run. Below is the list of the

three runs, the mean values, the standard deviation and percent relative standard deviation of

each solute on all six columns used. Compounds that are not listed on the table means they did

not elute or their boiling point exceeded the maximum temperature of the column used. Not all

illicit drugs ran on each column. The data for each column are shown in Table 3.1-3.6.

Table 3.1. Retention time (min) for column ZB Wax plus max temperature 250 °C (polyethylene glycol) column

Solute Run1 Run2 Run3 Avg Stdev %RSD 1,2-Dibromoethane 6.643 6.647 6.648 6.646 0.003 0.040 1,2-Dichlorobenzene 9.343 9.340 9.340 9.341 0.002 0.019 1,2-Dimethylbenzene 6.492 6.480 6.485 6.486 0.006 0.093 1-Bromohexane 6.100 6.113 6.110 6.108 0.007 0.111 1-Bromopropane 2.888 2.887 2.888 2.888 0.001 0.020 1-Butanol 5.552 5.562 5.555 5.556 0.005 0.092 1-Nonene 3.497 3.492 3.497 3.495 0.003 0.083 1-Octanol 9.348 9.350 9.355 9.351 0.004 0.039 1-Octene 2.613 2.615 2.615 2.614 0.001 0.044 2- Propanol 3.423 3.428 3.420 3.424 0.004 0.118 2-Acetylpyridine 10.290 10.283 10.285 10.286 0.004 0.035 2-Butanone 3.925 3.913 3.915 3.918 0.006 0.164 2-Butoxyethanol 8.110 8.108 8.112 8.110 0.002 0.025 2-Chlorophenol 12.135 12.138 12.140 12.138 0.003 0.021 2-Methyl -2-Pentanol 5.108 5.103 5.115 5.109 0.006 0.118 2-Picoline 6.827 6.822 6.815 6.821 0.006 0.088 3-Amino-1-propanol 9.682 9.668 9.663 9.671 0.010 0.102 4-Chlorophenol 15.358 15.363 15.365 15.362 0.004 0.023 4-Methyl-2 pentanol 5.813 5.815 5.813 5.814 0.001 0.020 4-Nitrotoluene 11.897 11.898 11.898 11.898 0.001 0.005 Acetamide 11.358 11.357 11.362 11.359 0.003 0.023 Acetic Acid 9.142 9.137 9.102 9.127 0.022 0.239 Acetic anhydride 6.598 6.620 6.612 6.610 0.011 0.168

37

Acetone 3.195 3.195 3.195 3.195 0.000 0.000 Acetophenone 10.635 10.645 10.648 10.643 0.007 0.064 Alpha pinene 4.823 4.815 4.812 4.817 0.006 0.118 Amyl acetate 6.310 6.310 6.302 6.307 0.005 0.073 Aniline 11.377 11.378 11.382 11.379 0.003 0.023 Benzene 4.013 4.010 4.007 4.010 0.003 0.075 Benzoic Acid 15.733 15.755 15.748 15.745 0.011 0.071 Benzonitrile 10.305 10.307 10.307 10.306 0.001 0.011 Benzyl bromide 10.122 10.115 10.122 10.120 0.004 0.040 Benzyl chloride 9.538 9.537 9.532 9.536 0.003 0.034 Biphenyl 12.667 12.663 12.663 12.664 0.002 0.018 Bromobenzene 8.053 8.053 8.057 8.054 0.002 0.029 Butyric acid 9.707 9.712 9.718 9.712 0.006 0.057 Butyronitrile 5.130 5.135 5.135 5.133 0.003 0.056 Chlorobenzene 6.755 6.755 6.755 6.755 0.000 0.000 Cyclohexane 3.328 3.348 3.362 3.346 0.017 0.511 Cyclohexanol 8.167 8.170 8.168 8.168 0.002 0.019 Diiodomethane 7.037 7.048 7.032 7.039 0.008 0.116 Diisopropylamine 3.273 3.270 3.277 3.273 0.004 0.107 Dimethyl carbonate 4.018 4.035 4.043 4.032 0.013 0.317 Ethanol 3.975 3.977 3.977 3.976 0.001 0.029 Ethanolamine 8.040 8.008 8.100 8.049 0.047 0.580 Ethyl Acetate 3.592 3.593 3.590 3.592 0.002 0.043 Ethyl Acetoacetate 8.538 8.610 8.593 8.580 0.038 0.439 Ethyl benzoate 10.733 10.733 10.737 10.734 0.002 0.022 Ethyl decanoate 10.402 10.417 10.413 10.411 0.008 0.075 Ethylbenzene 5.402 5.398 5.399 5.400 0.002 0.039 Ethylene glycol 10.095 10.095 10.047 10.079 0.028 0.275 Formamide 10.085 10.087 10.085 10.086 0.001 0.011 Formic acid 3.342 3.280 3.398 3.340 0.059 1.767 Iodobenzene 9.135 9.128 9.133 9.132 0.004 0.039 Isoquinoline 13.078 13.092 13.090 13.087 0.008 0.058 Lactic acid 7.715 7.708 7.715 7.713 0.004 0.052 L-menthol 9.993 9.995 9.993 9.994 0.001 0.012 Malonic acid 8.425 8.430 8.428 8.428 0.003 0.030 Mesitylene 7.082 7.083 7.082 7.082 0.001 0.008 Methyl Acetate 3.252 3.255 3.252 3.253 0.002 0.053 Methyl Benzoate 10.413 10.410 10.407 10.410 0.003 0.029 Methyl isobutyl ketone 4.607 4.608 4.617 4.611 0.006 0.119

38

Methyl cyclohexane 7.725 7.727 7.730 7.727 0.003 0.033 Morpholine 7.110 7.107 7.108 7.108 0.002 0.021 N,N dimethylacetamide 8.235 8.238 8.242 8.238 0.004 0.043 N,N-Diethylaniline 10.385 10.387 10.380 10.384 0.004 0.035 N,N-Dimethylaniline 9.817 9.815 9.817 9.816 0.001 0.012 N,N-Dimethylformamide 7.935 7.928 7.927 7.930 0.004 0.055 Naphthalene 11.348 11.348 11.352 11.349 0.002 0.020 Nitrobenzene 11.327 11.330 11.332 11.330 0.003 0.022 Nitromethane 11.897 11.898 11.898 11.898 0.001 0.005 Nonylamine 8.697 8.690 8.702 8.696 0.006 0.069 N,propyl alcohol 3.852 3.918 3.940 3.903 0.046 1.173 o-anisaldehyde 12.533 12.545 12.540 12.539 0.006 0.048 Octanoic acid 12.923 12.927 12.927 12.926 0.002 0.018 Octylamine 7.857 7.842 7.840 7.846 0.009 0.118 Pentan-1-ol 7.047 7.050 7.045 7.047 0.003 0.036 Phenol 13.317 13.322 13.323 13.321 0.003 0.024 Phenylacetic Acid 15.908 15.900 15.893 15.900 0.008 0.047 Piperidine 4.698 4.688 4.688 4.691 0.006 0.123 Propanoic Acid 9.105 9.100 9.102 9.102 0.003 0.028 Propionitrile 4.380 4.383 4.380 4.381 0.002 0.040 Propylene Carbonate 12.072 12.078 12.068 12.073 0.005 0.042 Pyrazine 6.190 6.197 6.198 6.195 0.004 0.070 Pyridine 6.455 6.460 6.463 6.459 0.004 0.063 Pyrrole 9.010 9.095 9.120 9.075 0.058 0.635 Quinoline 12.787 12.780 12.778 12.782 0.005 0.037 Tetrachloroethylene 4.792 4.777 4.775 4.781 0.009 0.194 Tetrahydrofuran 3.467 3.468 3.470 3.468 0.002 0.044 Toluene 4.967 4.952 4.947 4.955 0.010 0.210 Triethyl amine 3.290 3.298 3.302 3.297 0.006 0.185

Table 3.2. Retention time (min) for ZB –35 (35% Phenyl 65% dimethyl polysiloxane) columns Solute Run1 Run2 Run3 Avg Stdev %RSD 1 -Chloronaphthalene 11.783 11.762 11.665 11.737 0.063 0.536 1,2-Dibromoethane 4.995 4.993 4.992 4.993 0.002 0.031 1,2-Dichlorobenzene 8.082 8.100 8.087 8.090 0.009 0.115 1,2-Dimethylbenzene 6.185 6.183 6.187 6.185 0.002 0.032 1,3,5-Trimethylbenzene 6.920 6.912 6.913 6.915 0.004 0.063 1-Bromohexane 6.468 6.463 6.458 6.463 0.005 0.077

39

1-Bromopropane 2.840 2.840 2.842 2.841 0.001 0.041 1-Butanol 3.167 3.155 3.152 3.158 0.008 0.251 1-Nitronaphthalene 13.948 13.948 13.950 13.949 0.001 0.008 1-Nonene 4.850 4.848 4.848 4.849 0.001 0.024 1-Octanol 7.580 7.580 7.582 7.581 0.001 0.015 1-Octene 3.720 3.723 3.723 3.722 0.002 0.047 2 -Methyl -2 propanol 2.418 2.422 2.415 2.418 0.004 0.145 2-Propanol 2.327 2.328 2.328 2.328 0.001 0.025 2-Acetylpyridine 8.352 8.328 8.339 8.340 0.012 0.144 2-Butanone 3.372 3.380 3.380 3.377 0.005 0.137 2-Butoxyethanol 5.865 5.980 5.925 5.923 0.058 0.971 2-Chlorobenzoic acid 11.548 11.517 11.528 11.531 0.016 0.136 2-Chlorophenol 7.588 7.587 7.582 7.586 0.003 0.042 2-Methyl -2-Pentanol 3.618 3.618 3.615 3.617 0.002 0.048 2-Picoline 5.605 5.627 5.618 5.617 0.011 0.197 4-Chlorophenol 9.700 9.707 9.705 9.704 0.004 0.037 4-Methyl-2 pentanol 4.315 4.315 4.312 4.314 0.002 0.040 4-Nitrophenol 13.168 13.167 13.162 13.166 0.003 0.024 4-Nitrotoluene 9.857 9.852 9.853 9.854 0.003 0.027 Acenaphthene 12.698 12.695 12.692 12.695 0.003 0.024 Acetanilide 12.018 12.015 12.010 12.014 0.004 0.034 Acetic Acid 3.438 3.395 3.465 3.433 0.035 1.028 Acetic anhydride 4.143 4.133 4.128 4.135 0.008 0.185 Acetone 2.978 2.960 2.952 2.963 0.013 0.449 Acetophenone 8.738 8.727 8.740 8.735 0.007 0.080 Alpha pinene 6.138 6.132 6.130 6.133 0.004 0.068 Amyl acetate 6.245 6.242 6.233 6.240 0.006 0.100 Aniline 7.813 7.828 7.817 7.819 0.008 0.099 Aspirin 10.008 10.008 10.008 10.008 0.000 0.000 Benzene 3.767 3.770 3.765 3.767 0.003 0.067 Benzoic Acid 9.533 9.548 9.508 9.530 0.020 0.212 Benzonitrile 7.948 7.948 7.947 7.948 0.001 0.007 Benzophenone 13.937 13.938 13.932 13.936 0.003 0.023 Benzyl alcohol 7.913 7.960 7.958 7.944 0.027 0.335 Benzyl bromide 8.635 8.628 8.623 8.629 0.006 0.070 Benzyl chloride 7.980 7.980 7.988 7.983 0.005 0.058 Biphenyl 11.625 11.632 11.630 11.629 0.004 0.031 Butyric acid 4.047 4.043 4.050 4.047 0.004 0.087 Butyronitrile 4.062 4.065 4.068 4.065 0.003 0.074

40

Chlorobenzene 5.730 5.735 5.727 5.731 0.004 0.071 Cyclohexane 2.883 2.875 2.873 2.877 0.005 0.184 Cyclohexanol 5.797 5.783 5.802 5.794 0.010 0.170 Diisopropylamine 3.182 3.182 3.182 3.182 0.000 0.000 Dimethyl carbonate 2.978 2.978 2.978 2.978 0.000 0.000 Ethanol 2.827 2.833 2.830 2.830 0.003 0.106 Ethanolamine 3.755 3.835 3.890 3.827 0.068 1.774 Ethyl Acetate 3.377 3.377 3.375 3.376 0.001 0.034 Ethyl benzoate 9.522 9.527 9.527 9.525 0.003 0.030 Ethyl decanoate 10.812 10.815 10.788 10.805 0.015 0.137 Ethylbenzene 5.623 5.627 5.627 5.626 0.002 0.041 Ethylene glycol 4.035 4.008 3.962 4.002 0.037 0.922 Formamide 6.693 6.692 6.658 6.681 0.020 0.298 Iodobenzene 7.887 7.892 7.897 7.892 0.005 0.063 Isopentyl acetate 5.793 5.782 5.777 5.784 0.008 0.142 Isoquinoline 10.858 10.845 10.848 10.850 0.007 0.063 Lactic acid 4.527 4.527 4.522 4.525 0.003 0.064 L-menthol 8.670 8.670 8.667 8.669 0.002 0.020 m, Toluic acid 10.405 10.408 10.432 10.415 0.015 0.142 Methyl Acetate 3.015 3.017 3.016 3.016 0.001 0.033 Methyl isobutyl ketone 4.403 4.410 4.415 4.409 0.006 0.137 Methyl-4-hydroxybenzoate 12.380 12.383 12.387 12.383 0.004 0.028 Morpholine 5.418 5.412 5.425 5.418 0.007 0.120 N,N dimethylacetamide 6.268 6.250 6.243 6.254 0.013 0.206 N,N-diethylaniline 9.940 9.935 9.942 9.939 0.004 0.036 Naphthalene 9.858 9.858 9.857 9.858 0.001 0.006 Nitrobenzene 9.048 9.052 9.048 9.049 0.002 0.026 Nitromethane 2.873 2.853 2.855 2.860 0.011 0.385 Nonylamine 8.540 8.537 8.530 8.536 0.005 0.060 o-anisaldehyde 11.250 11.232 11.228 11.237 0.012 0.104 O-cresol 8.322 8.300 8.312 8.311 0.011 0.133 Octanoic acid 8.095 8.095 8.093 8.094 0.001 0.014 Octylamine 7.507 7.507 7.498 7.504 0.005 0.069 Pentan-1-ol 4.578 4.572 4.577 4.576 0.003 0.070 Phenol 7.462 7.472 7.455 7.463 0.009 0.114 Phenyl acetic Acid 10.375 10.385 10.380 10.380 0.005 0.048 Piperidine 4.482 4.480 4.478 4.480 0.002 0.045 Propanoic Acid 4.020 4.055 4.060 4.045 0.022 0.539 Propionitrile 2.893 2.900 2.898 2.897 0.004 0.124

41

Pyrazine 4.277 4.287 4.283 4.282 0.005 0.118 Pyridine 4.892 4.880 4.877 4.883 0.008 0.163 Pyrrole 4.463 4.458 4.465 4.462 0.004 0.081 Quinoline 10.642 10.662 10.647 10.650 0.010 0.098 Resorcinol 10.868 10.862 10.860 10.863 0.004 0.038 Tetrachloroethylene 5.038 5.042 5.038 5.039 0.002 0.046 Toluene 4.737 4.732 4.730 4.733 0.004 0.076 Triethyl amine 3.330 3.327 3.323 3.327 0.004 0.106 Vanillin 12.137 12.145 12.137 12.140 0.005 0.038

Table 3.3. Retention time for TR 1 MS (100% dimethyl polysiloxane) column Solute Run1 Run 2 Run 3 Average Stdev %RSD 1,2-Dibromoethane 4.375 4.378 4.373 4.375 0.003 0.058 1,2-Dichlorobenzene 9.143 9.150 9.150 9.148 0.004 0.044 1,3,5-Trimethylbenzene 8.620 8.623 8.622 8.622 0.002 0.018 1-Bromohexane 8.038 8.042 8.047 8.042 0.005 0.056 1-Bromopropane 2.725 2.718 2.723 2.722 0.004 0.132 1-Butanol 3.263 3.270 3.267 3.267 0.004 0.108 1-Chloronaphthalene 12.572 12.558 12.560 12.563 0.008 0.060 1-Nitronaphthalene 14.257 14.260 14.258 14.258 0.002 0.011 1-Nonene 5.728 5.743 5.748 5.740 0.010 0.181 1-Octanol 7.818 7.820 7.832 7.823 0.008 0.097 1-Octene 4.462 4.463 4.460 4.462 0.002 0.034 2 - Methyl -2 propanol 2.507 2.502 2.495 2.501 0.006 0.241 2 Propanol 2.202 2.200 2.200 2.201 0.001 0.052 2-Acetylpyridine 9.003 8.997 8.997 8.999 0.003 0.038 2-Butanone 4.475 4.485 4.478 4.479 0.005 0.115 2-Butoxyethanol 5.913 5.910 5.912 5.912 0.002 0.026 2-Chlorophenol 8.678 8.683 8.678 8.680 0.003 0.033 2-Methyl -2-Pentanol 3.918 3.915 3.917 3.917 0.002 0.039 2-Picoline 6.575 6.573 6.572 6.573 0.002 0.023 4-Chlorophenol 9.012 9.007 9.008 9.009 0.003 0.029 4-Methyl-2 pentanol 4.163 4.165 4.167 4.165 0.002 0.048 4-Nitrotoluene 9.198 9.205 9.205 9.203 0.004 0.044 Acenaphthene 13.408 13.422 13.417 13.416 0.007 0.053 Acetanilide 12.295 12.257 12.250 12.267 0.024 0.197 Acetic Acid 4.653 4.638 4.658 4.650 0.010 0.224 Acetic anhydride 2.507 2.508 2.505 2.507 0.002 0.061 Acetone 4.322 4.225 4.128 4.225 0.097 2.296

42

Acetophenone 9.423 9.450 9.428 9.434 0.014 0.152 Alpha pinene 8.360 8.362 8.353 8.358 0.005 0.057 Amyl acetate 7.733 7.742 7.743 7.739 0.006 0.071 Aniline 8.395 8.400 8.400 8.398 0.003 0.034 Benzene 5.010 5.030 5.033 5.024 0.013 0.249 Benzoic Acid 10.485 10.495 10.503 10.494 0.009 0.086 Benzonitrile 8.415 8.405 8.400 8.407 0.008 0.091 Benzophenone 14.418 14.412 14.412 14.414 0.003 0.024 Benzyl alcohol 7.248 7.250 7.250 7.249 0.001 0.016 Benzyl bromide 8.032 8.027 8.027 8.029 0.003 0.036 Benzyl chloride 8.903 8.887 8.885 8.892 0.010 0.111 Biphenyl 12.467 12.465 12.467 12.466 0.001 0.009 Butyric acid 5.148 5.310 5.295 5.251 0.090 1.705 Butyronitrile 3.160 3.162 3.155 3.159 0.004 0.114 Chlorobenzene 8.152 8.145 8.147 8.148 0.004 0.044 Cyclohexane 3.328 3.323 3.313 3.321 0.008 0.230 Cyclohexanol 5.602 5.627 5.632 5.620 0.016 0.286 Diisopropylamine 3.275 3.273 3.272 3.273 0.002 0.047 Dimethyl carbonate 2.868 2.867 2.863 2.866 0.003 0.092 Ethanol 3.930 3.935 3.935 3.933 0.003 0.073 Ethanolamine 3.342 3.372 3.323 3.346 0.025 0.738 Ethyl Acetate 4.580 4.572 4.577 4.576 0.004 0.088 Ethyl Acetoacetate 6.103 6.110 6.115 6.109 0.006 0.099 Ethyl benzoate 10.515 10.502 10.495 10.504 0.010 0.097 Ethyl decanoate 12.503 12.500 12.498 12.500 0.003 0.020 Ethylbenzene 5.417 5.420 5.422 5.420 0.003 0.046 Ethylene glycol 3.658 3.658 3.765 3.694 0.062 1.672 Formamide 6.697 6.647 6.605 6.650 0.046 0.693 Iodobenzene 7.437 7.438 7.438 7.438 0.001 0.008 Isopentyl acetate 7.433 7.418 7.408 7.420 0.013 0.170 Isoquinoline 11.408 11.395 11.392 11.398 0.009 0.075 Lactic acid 7.547 8.065 7.613 7.742 0.282 3.642 L-menthol 8.862 8.860 8.860 8.861 0.001 0.013 Methyl Acetate 4.245 4.245 4.247 4.246 0.001 0.027 Methyl isobutyl ketone 5.710 5.705 5.703 5.706 0.004 0.063 Methyl-4-hydroxybenzoate 12.907 12.895 12.843 12.882 0.034 0.264 Morpholine 6.277 6.272 6.273 6.274 0.003 0.042 n-Propyl alcohol 4.080 4.085 4.080 4.082 0.003 0.071 N,N dimethylacetamide 5.232 5.240 5.232 5.235 0.005 0.088

43

N,N dimethylaniline 9.717 9.717 9.712 9.715 0.003 0.030 N,N-diethylaniline 11.068 11.063 11.067 11.066 0.003 0.024 Naphthalene 10.793 10.817 10.800 10.803 0.012 0.114 Nitrobenzene 9.653 9.633 9.635 9.640 0.011 0.114 Nonylamine 10.333 10.332 10.343 10.336 0.006 0.059 o-anisaldehyde 11.957 11.955 11.952 11.955 0.003 0.021 Octanoic acid 8.368 8.368 8.368 8.368 0.000 0.000 Octylamine 9.268 9.272 9.278 9.273 0.005 0.054 Pentan-1-ol 6.043 6.033 6.033 6.036 0.006 0.096 Phenanthrene 15.665 15.665 15.657 15.662 0.005 0.029 Phenol 8.468 8.470 8.473 8.470 0.003 0.030 Phenyl acetic Acid 11.187 11.187 11.185 11.186 0.001 0.010 Piperidine 4.173 4.178 4.173 4.175 0.003 0.069 Propionitrile 2.600 2.602 2.598 2.600 0.002 0.077 Pyrazine 3.597 3.598 3.602 3.599 0.003 0.074 Pyridine 5.725 5.737 5.723 5.728 0.008 0.132 Pyrrole 4.035 4.027 4.025 4.029 0.005 0.131 Quinoline 11.177 11.175 11.173 11.175 0.002 0.018 Resorcinol 11.353 11.373 11.403 11.376 0.025 0.221 Tetrachloroethylene 6.647 6.647 6.645 6.646 0.001 0.017 Toluene 6.103 6.100 6.100 6.101 0.002 0.028 Triethylamine 3.520 3.518 3.515 3.518 0.003 0.072 Vanillin 12.487 12.487 12.532 12.502 0.026 0.208 Xanthene 14.718 14.720 14.725 14.721 0.004 0.024

Table 3.4. Retention time for TR 5(5 % phenyl methyl polysiloxane) column Solute Run1 Run 2 Run 3 Avg Stdev %RSD 1-Chloronaphthalene 10.778 10.772 10.773 10.774 0.003 0.030 1,2-Dibromoethane 4.330 4.332 4.333 4.332 0.002 0.035 1,2-Dichlorobenzene 7.292 7.285 7.300 7.292 0.008 0.103 1,2-Dimethylbenzene 5.610 5.612 5.618 5.613 0.004 0.074 1,3,5-Trimethylbenzene 6.492 6.483 6.483 6.486 0.005 0.080 1-Bromohexane 6.113 6.108 6.107 6.109 0.003 0.053 1-Bromopropane 2.705 2.710 2.710 2.708 0.003 0.107 1-Butanol 2.638 2.632 2.637 2.636 0.003 0.122 1-Nitronaphthalene 12.570 12.570 12.572 12.571 0.001 0.009 1-Nonene 5.343 5.348 5.345 5.345 0.003 0.047 1-Octene 4.095 4.113 4.125 4.111 0.015 0.367 2-Propanol 2.215 2.263 2.267 2.248 0.029 1.287

44

2-Acetylpyridine 7.258 7.255 7.253 7.255 0.003 0.035 2-Butanone 2.675 2.647 2.645 2.656 0.017 0.632 2-Chlorobenzoic acid 10.612 10.652 10.600 10.621 0.027 0.256 2-Chlorophenol 6.760 6.760 6.767 6.762 0.004 0.060 2-Picoline 4.602 4.602 4.597 4.600 0.003 0.063 3-Amino-1-propanol 4.865 4.857 4.867 4.863 0.005 0.109 3-Nitrobenzoic acid 12.262 12.265 12.263 12.263 0.002 0.012 4-Chlorophenol 8.388 8.383 8.372 8.381 0.008 0.098 4-Methyl-2 pentanol 3.478 3.553 3.487 3.506 0.041 1.168 Acenaphthene 11.613 11.612 11.610 11.612 0.002 0.013 Acetanilide 10.608 10.608 10.605 10.607 0.002 0.016 Acetic Acid 2.873 2.863 2.867 2.868 0.005 0.176 Acetone 2.348 2.343 2.342 2.344 0.003 0.137 Acetophenone 7.657 7.668 7.672 7.666 0.008 0.101 Alpha pinene 6.140 6.132 6.135 6.136 0.004 0.066 Amyl acetate 5.808 5.812 5.808 5.809 0.002 0.040 Aniline 6.607 6.600 6.605 6.604 0.004 0.055 Benzoic Acid 9.100 9.160 9.128 9.129 0.030 0.329 Benzonitrile 6.685 6.690 6.698 6.691 0.007 0.098 Benzophenone 12.705 12.712 12.713 12.710 0.004 0.034 Benzyl alcohol 7.130 7.145 7.155 7.143 0.013 0.176 Benzyl chloride 7.007 7.003 7.007 7.006 0.002 0.033 Biphenyl 10.690 10.688 10.683 10.687 0.004 0.034 Butyronitrile 2.738 2.710 2.720 2.723 0.014 0.521 Chlorobenzene 5.008 5.003 5.008 5.006 0.003 0.058 Cyclohexane 2.605 2.607 2.602 2.605 0.003 0.097 Cyclohexanol 4.975 4.988 4.985 4.983 0.007 0.137 Diisopropylamine 2.603 2.592 2.585 2.593 0.009 0.350 Ethanol 2.300 2.270 2.273 2.281 0.017 0.724 Ethyl Acetate 2.727 2.691 2.718 2.712 0.019 0.691 Ethyl benzoate 8.733 8.735 8.730 8.733 0.003 0.029 Ethyl decanoate 10.685 10.685 10.687 10.686 0.001 0.011 Ethylbenzene 4.618 4.618 4.620 4.619 0.001 0.025 Formamide 4.947 4.950 4.952 4.950 0.003 0.051 Iodobenzene 6.775 6.770 6.787 6.777 0.009 0.129 Isopentyl acetate 5.400 5.392 5.390 5.394 0.005 0.098 Isoquinoline 9.665 9.665 9.655 9.662 0.006 0.060 Lactic acid 5.803 6.092 5.880 5.925 0.150 2.526 L-menthol 8.530 8.532 8.527 8.530 0.003 0.030

45

Methyl Acetate 2.425 2.412 2.417 2.418 0.007 0.271 Methyl isobutyl ketone 3.748 3.743 3.745 3.745 0.003 0.067 Methyl-4-hydroxybenzoate 11.228 11.217 11.220 11.222 0.006 0.051 Morpholine 4.492 4.492 4.490 4.491 0.001 0.026 n-Propyl alcohol 2.513 2.333 2.337 2.394 0.103 4.293 N,N dimethylaniline 7.895 7.897 7.895 7.896 0.001 0.015 N,N-Diethylaniline 9.253 9.255 9.255 9.254 0.001 0.012 Naphthalene 8.897 8.902 8.893 8.897 0.005 0.051 Nitrobenzene 7.937 7.940 7.935 7.937 0.003 0.032 Nitromethane 2.148 2.182 2.187 2.172 0.021 0.977 Nonylamine 8.418 8.415 8.413 8.415 0.003 0.030 o-anisaldehyde 9.413 9.415 9.415 9.414 0.001 0.012 Octylamine 7.313 7.297 7.295 7.302 0.010 0.135 Pentan-1-ol 4.058 4.058 4.067 4.061 0.005 0.128 Phenanthrene 13.943 13.945 13.940 13.943 0.003 0.018 Phenol 6.607 6.620 6.617 6.615 0.007 0.103 Phenyl acetic Acid 9.398 9.423 9.393 9.405 0.016 0.171 Piperidine 3.472 3.480 3.478 3.477 0.004 0.120 Propanoic Acid 3.835 3.827 3.852 3.838 0.013 0.333 Propionitrile 2.203 2.202 2.198 2.201 0.003 0.120 Pyridine 3.778 3.797 3.795 3.790 0.010 0.275 Pyrrole 3.533 3.528 3.507 3.523 0.014 0.392 Quinoline 9.428 9.437 9.437 9.434 0.005 0.055 Resorcinol 9.685 9.680 9.687 9.684 0.004 0.037 Tetrachloroethylene 4.572 4.572 4.572 4.572 0.000 0.000 Toluene 4.015 4.003 3.997 4.005 0.009 0.229 Triethylamine 2.778 2.773 2.767 2.773 0.006 0.199 Vanillin 10.818 10.817 10.820 10.818 0.002 0.014 Xanthene 12.960 12.973 12.975 12.969 0.008 0.063

Table 3.5. Retention time for TG 5- MS (5% diphenyl 95% dimethyl polysiloxane) column Solute Run1 Run 2 Run 3 Avg Stdev %RSD 1,2-Dichlorobenzene 7.227 7.225 7.232 7.228 0.004 0.050 1,2-Dimethylbenzene 5.488 5.488 5.488 5.488 0.000 0.000 1,3,5-Trimethylbenzene 6.403 6.398 6.403 6.401 0.003 0.045 1,2- Dibromoethane 4.330 4.332 4.333 4.332 0.002 0.035 1-Bromohexane 5.985 5.985 5.985 5.985 0.000 0.000 1-Bromopropane 2.705 2.710 2.710 2.708 0.003 0.107

46

1-Butanol 3.042 3.048 3.060 3.050 0.009 0.300 1-Nitronaphthalene 12.502 12.500 12.498 12.500 0.002 0.016 1-Nonene 5.343 5.348 5.345 5.345 0.003 0.047 1-Octene 4.095 4.113 4.125 4.111 0.015 0.367 2-Methyl -2 propanol 2.352 2.340 2.338 2.343 0.008 0.323 2-Propanol 2.215 2.263 2.267 2.248 0.029 1.287 2-Acetylpyridine 7.152 7.158 7.153 7.154 0.003 0.045 2-Butanone 2.562 2.560 2.645 2.589 0.049 1.874 2-Butoxyethanol 5.718 5.723 5.715 5.719 0.004 0.071 2-Chlorobenzoic acid 10.452 10.478 10.462 10.464 0.013 0.125 2-Chlorophenol 6.680 6.678 6.673 6.677 0.004 0.054 2-Methyl -2-Pentanol 3.648 3.685 3.658 3.664 0.019 0.522 2-Picoline 4.452 4.460 4.467 4.460 0.008 0.168 3-Amino-1-propanol 4.800 4.737 4.812 4.783 0.040 0.842 3-Nitrobenzoic acid 12.155 12.168 12.175 12.166 0.010 0.083 4-Chlorophenol 8.902 8.892 8.888 8.894 0.007 0.081 4-Methyl-2 pentanol 3.970 3.970 3.982 3.974 0.007 0.174 4-Nitrophenol 11.752 11.752 11.752 11.752 0.000 0.000 Acenaphthene 11.566 11.555 11.552 11.558 0.007 0.064 Acetanilide 10.537 10.548 10.535 10.540 0.007 0.066 Acetic Acid 2.678 2.687 2.688 2.684 0.006 0.205 Acetone 2.222 2.222 2.220 2.221 0.001 0.052 Acetophenone 7.592 7.582 7.580 7.585 0.006 0.085 Amyl acetate 5.722 5.717 5.717 5.719 0.003 0.050 Aniline 6.552 6.550 6.548 6.550 0.002 0.031 Aspirin 9.915 9.932 9.942 9.930 0.014 0.137 Benzene 2.987 2.990 2.982 2.986 0.004 0.135 Benzoic Acid 9.032 9.020 9.070 9.041 0.026 0.289 Benzonitrile 6.633 6.640 6.633 6.635 0.004 0.061 Benzophenone 12.533 12.650 12.655 12.613 0.069 0.547 Benzyl alcohol 7.130 7.145 7.155 7.143 0.013 0.176 Benzyl bromide 7.967 7.970 7.962 7.966 0.004 0.051 Benzyl chloride 6.972 6.967 6.967 6.969 0.003 0.041 Biphenyl 10.647 10.637 10.637 10.640 0.006 0.054 Butyronitrile 3.095 3.108 3.107 3.103 0.007 0.233 Chlorobenzene 4.893 4.903 4.897 4.898 0.005 0.103 Cyclohexane 3.012 3.015 3.010 3.012 0.003 0.084 Cyclohexanol 5.492 5.522 5.502 5.505 0.015 0.277 Diisopropylamine 2.995 2.990 2.988 2.991 0.004 0.121

47

Dimethyl carbonate 2.712 2.713 2.717 2.714 0.003 0.097 Ethanol 2.150 2.150 2.155 2.152 0.003 0.134 Ethanolamine 3.127 3.167 3.132 3.142 0.022 0.694 Ethyl Acetate 2.648 2.647 2.652 2.649 0.003 0.100 Ethyl benzoate 8.638 8.652 8.645 8.645 0.007 0.081 Ethyl decanoate 10.603 10.605 10.610 10.606 0.004 0.034 Ethylbenzene 5.182 5.187 5.188 5.186 0.003 0.062 Formamide 5.158 5.132 5.115 5.135 0.022 0.422 Iodobenzene 7.348 7.343 7.340 7.344 0.004 0.055 Isopentyl acetate 5.293 5.255 5.237 5.262 0.029 0.543 Isoquinoline 9.595 9.588 9.582 9.588 0.007 0.068 Lactic acid 3.927 3.930 3.883 3.913 0.026 0.672 L-menthol 8.530 8.532 8.527 8.530 0.003 0.030 Methyl Acetate 2.317 2.302 2.293 2.304 0.012 0.526 Methyl isobutyl ketone 3.662 3.680 3.662 3.668 0.010 0.283 Methyl-4-hydroxybenzoate 11.133 11.125 11.125 11.128 0.005 0.042 Morpholine 4.250 4.252 4.245 4.249 0.004 0.085 n-Propyl alcohol 2.223 2.222 2.218 2.221 0.003 0.119 N,N- dimethylacetamide 5.248 5.242 5.258 5.249 0.008 0.154 N,N- dimethylaniline 7.842 7.823 7.830 7.832 0.010 0.123 N,N-Diethylaniline 9.172 9.173 9.170 9.172 0.002 0.017 Naphthalene 8.838 8.833 8.837 8.836 0.003 0.030 Nitrobenzene 7.835 7.825 7.827 7.829 0.005 0.068 Nitromethane 2.473 2.465 2.460 2.466 0.007 0.266 Nonylamine 8.313 8.307 8.310 8.310 0.003 0.036 o-anisaldehyde 10.172 10.173 10.172 10.172 0.001 0.006 o-cresol 7.378 7.368 7.375 7.374 0.005 0.070 Octylamine 7.228 7.232 7.230 7.230 0.002 0.028 Pentan-1-ol 3.932 3.932 3.930 3.931 0.001 0.029 Phenanthrene 13.830 13.825 13.827 13.827 0.003 0.018 Phenol 6.530 6.525 6.513 6.523 0.009 0.134 Phenyl acetic Acid 9.440 9.432 9.427 9.433 0.007 0.070 Piperidine 3.943 3.948 3.943 3.945 0.003 0.073 Propanoic Acid 3.835 3.827 3.852 3.838 0.013 0.333 Propionitrile 2.525 2.528 2.527 2.527 0.002 0.060 Pyridine 3.705 3.698 3.698 3.700 0.004 0.109 Pyrrole 3.900 3.900 3.903 3.901 0.002 0.044 Quinoline 9.367 9.363 9.372 9.367 0.005 0.048 Resorcinol 9.578 9.580 9.575 9.578 0.003 0.026

48

Tetrachloroethylene 4.482 4.478 4.475 4.478 0.004 0.078 Toluene 3.977 3.972 3.970 3.973 0.004 0.091 Triethylamine 3.205 3.200 3.198 3.201 0.004 0.113 Vanillin 10.737 10.730 10.733 10.733 0.004 0.033

Table 3.6. Retention time (min) for TG 1301 MS (6% cyanopropylphenyl 94% dimethyl polysiloxane) column

Solute Run1 Run 2 Run 3 Avg Stdev %RSD 1-Chloronaphthalene 11.177 11.158 11.153 11.163 0.013 0.113 1,2-Dibromoethane 4.780 4.780 4.775 4.778 0.003 0.060 1,2-Dichlorobenzene 7.565 7.567 7.563 7.565 0.002 0.026 1,2-Dimethylbenzene 5.705 5.718 5.723 5.715 0.009 0.163 1,3,5-trimethylbenzene 6.577 6.573 6.565 6.572 0.006 0.093 1-Bromohexane 6.248 6.242 6.243 6.244 0.003 0.051 1-Bromopropane 2.760 2.767 2.772 2.766 0.006 0.218 1-Butanol 3.503 3.487 3.482 3.491 0.011 0.314 1-Nonene 5.332 5.333 5.333 5.333 0.001 0.011 1-Octanol 8.050 8.043 8.048 8.047 0.004 0.045 1-Octene 4.117 4.118 4.118 4.118 0.001 0.014 2-MEthyl -2 propanol 2.503 2.497 2.492 2.497 0.006 0.221 2-Propanol 2.333 2.345 2.352 2.343 0.010 0.410 2-Acetylpyridine 7.722 7.720 7.725 7.722 0.003 0.033 2-Butanone 2.897 2.900 2.898 2.898 0.002 0.053 2-Butoxyethanol 6.172 6.178 6.177 6.176 0.003 0.052 2-Chlorophenol 7.467 7.463 7.470 7.467 0.004 0.047 2-Methyl -2-Pentanol 4.095 4.078 4.085 4.086 0.009 0.209 2-Picoline 4.872 4.870 4.875 4.872 0.003 0.052 3-Amino-1-propanol 5.713 5.732 5.728 5.724 0.010 0.175 4-Chlorophenol 6.195 6.197 6.195 6.196 0.001 0.019 4-Methyl-2 pentanol 4.460 4.457 4.448 4.455 0.006 0.140 4-Nitrotoluene 9.752 9.750 9.750 9.751 0.001 0.012 Acenaphthene 12.003 12.000 11.995 11.999 0.004 0.034 Acetic Acid 3.442 3.425 3.417 3.428 0.013 0.372 Acetic anhydride 4.262 4.258 4.262 4.261 0.002 0.054 Acetophenone 8.240 8.238 8.238 8.239 0.001 0.014 Alpha pinene 5.985 5.980 5.980 5.982 0.003 0.048 Amyl acetate 6.105 6.108 6.102 6.105 0.003 0.049 Aniline 7.398 7.400 7.403 7.400 0.003 0.034 Benzene 3.187 3.187 3.185 3.186 0.001 0.036

49

Benzoic Acid 10.032 10.150 10.045 10.076 0.065 0.642 Benzonitrile 7.432 7.432 7.430 7.431 0.001 0.016 Benzyl alcohol 8.005 8.018 8.018 8.014 0.008 0.094 Benzyl bromide 8.285 8.295 8.292 8.291 0.005 0.062 Benzyl chloride 7.408 7.412 7.418 7.413 0.005 0.068 Biphenyl 11.038 11.047 11.050 11.045 0.006 0.057 Butyric acid 5.685 5.750 5.728 5.721 0.033 0.578 Butyronitrile 3.688 3.688 3.685 3.687 0.002 0.047 Chlorobenzene 5.175 5.175 5.180 5.177 0.003 0.056 Cyclohexane 2.965 2.947 2.947 2.953 0.010 0.352 Cyclohexanol 6.030 6.052 6.050 6.044 0.012 0.201 Diisopropylamine 3.007 3.005 3.005 3.006 0.001 0.038 Ethanol 2.362 2.358 2.360 2.360 0.002 0.085 Ethanolamine 3.867 3.852 3.860 3.860 0.008 0.194 Ethyl Acetate 2.902 2.903 2.902 2.902 0.001 0.020 Ethyl Acetoacetate 6.715 6.720 6.717 6.717 0.003 0.037 Ethyl benzoate 9.115 9.122 9.138 9.125 0.012 0.129 Ethyl decanoate 10.952 10.952 10.943 10.949 0.005 0.047 Ethyl benzene 5.253 5.258 5.252 5.254 0.003 0.061 Ethylene glycol 4.597 4.522 4.713 4.611 0.096 2.087 Formamide 6.375 6.387 6.376 6.379 0.007 0.104 Iodobenzene 7.528 7.525 7.525 7.526 0.002 0.023 Isoquinoline 10.243 10.252 10.262 10.252 0.010 0.093 Lactic acid 4.513 4.505 4.495 4.504 0.009 0.200 L-menthol 9.013 9.010 9.003 9.009 0.005 0.057 Malonic acid 8.510 8.505 8.508 8.508 0.003 0.030 Methyl isobutyl ketone 4.137 4.132 4.133 4.134 0.003 0.064 Morpholine 4.912 4.925 4.903 4.913 0.011 0.225 n-Propyl alcohol 2.465 2.465 2.462 2.464 0.002 0.070 N,N- dimethylacetamide 6.207 6.210 6.208 6.208 0.002 0.025 N,N- dimethylaniline 8.237 8.233 8.237 8.236 0.002 0.028 N,N-diethylaniline 9.577 9.593 9.568 9.579 0.013 0.132 Naphthalene 9.313 9.320 9.320 9.318 0.004 0.043 Nitrobenzene 8.543 8.543 8.538 8.541 0.003 0.034 Nitromethane 2.860 2.855 2.852 2.856 0.004 0.142 Nonylamine 8.538 8.537 8.542 8.539 0.003 0.031 o-anisaldehyde 10.675 10.677 10.677 10.676 0.001 0.011 o-cresol 8.512 8.518 8.522 8.517 0.005 0.059 Octanoic acid 9.532 9.557 9.527 9.539 0.016 0.169

50

Octylamine 7.430 7.428 7.433 7.430 0.003 0.034 Pentan-1-ol 4.580 4.580 4.580 4.580 0.000 0.000 Phenol 7.978 7.970 7.963 7.970 0.008 0.094 Piperidine 4.057 4.062 4.058 4.059 0.003 0.065 Propanoic Acid 4.567 4.573 4.548 4.563 0.013 0.286 Propionitrile 2.900 2.903 2.905 2.903 0.003 0.087 Pyridine 4.152 4.147 4.145 4.148 0.004 0.087 Pyrrole 4.790 4.795 4.803 4.796 0.007 0.137 Quinoline 9.955 9.950 9.958 9.954 0.004 0.041 Tetrachloroethylene 4.550 4.542 4.542 4.545 0.005 0.102 Toluene 4.165 4.163 4.163 4.164 0.001 0.028 Triethylamine 3.178 3.173 3.170 3.174 0.004 0.127

Table 3.7. Experimental gas-to-liquid partition coefficient data (E, S, A, B, and L) from the literature [50, 52-53].

SOLUTE E S A B L 1-Butanol 0.224 0.420 0.370 0.480 2.601 1,2-Dibromoethane 0.747 0.760 0.100 0.170 3.382 1,2-Dichlorobenzene 0.872 0.780 0.000 0.040 4.518 1,2-Dimethylbenzene 0.663 0.560 0.000 0.160 3.939 1,3,5-Trimethylbenzene 0.649 0.520 0.000 0.190 4.344 1-Bromohexane 0.349 0.400 0.000 0.120 4.130 1-Bromopropane 0.366 0.400 0.000 0.120 2.620 1-Chloronaphthalene 1.417 1.000 0.000 0.140 5.856 1-Nitronaphthalene 1.600 1.590 0.000 0.290 7.056 1-Nonene 0.090 0.080 0.000 0.070 4.073 1-Octanol 0.199 0.420 0.370 0.480 4.619 1-Octene 0.094 0.080 0.000 0.070 3.568 2 Methyl-2- pentanol 0.169 0.300 0.310 0.640 3.240 2 Methyl-2-propanol 0.180 0.300 0.310 0.600 1.963 2-Propanol 0.212 0.360 0.330 0.560 1.764 2-Acetylpyridine 0.730 1.090 0.000 0.620 4.425 2-Bromophenol 1.037 0.850 0.350 0.300 4.802 2-Butanone 0.166 0.700 0.000 0.510 2.287 2-Butoxyethanol 0.201 0.530 0.260 0.830 3.656 2-Chlorobenzoic acid 0.840 1.010 0.680 0.400 4.840 2-Chlorophenol 0.853 0.880 0.320 0.310 4.178 2-Methyl-1-propanol 0.217 0.390 0.370 0.480 2.413 2-Naphthol 1.520 1.080 0.610 0.400 6.200

51

2-Octanol 0.158 0.360 0.330 0.360 1.295 2-Picoline 0.598 0.750 0.000 0.580 3.422 3-Amino-1-propanol 0.465 0.850 0.380 0.950 3.016 3-Nitrobenzoic acid 0.990 1.130 0.730 0.530 5.535 4-Chlorophenol 0.915 1.080 0.670 0.200 4.775 4-Methyl-2-pentanol 0.167 0.330 0.330 0.550 3.263 4-Nitrophenol 1.070 1.720 0.820 0.260 5.876 4-Nitrotoluene 0.870 1.110 0.000 0.280 5.154 Acenaphthene 1.604 1.050 0.000 0.220 6.469 Acetamide 0.460 1.300 0.550 0.690 2.990 Acetanilide 0.900 1.370 0.400 0.670 5.570 Acetic Acid 0.265 0.640 0.620 0.440 1.816 Acetic Anhydride 0.174 0.800 0.080 0.730 2.735 Acetone 0.179 0.700 0.040 0.490 1.696 Acetophenone 0.818 1.010 0.000 0.480 4.501 Alpha pinene 0.446 0.140 0.000 0.120 4.308 Amyl acetate 0.067 0.600 0.000 0.450 3.844 Aniline 0.955 0.960 0.260 0.410 3.934 Aspirin 0.781 1.690 0.710 0.670 6.279 Benzene 0.610 0.520 0.000 0.140 2.786 Benzoic Acid 0.730 0.900 0.590 0.400 4.657 Benzonitrile 0.742 1.110 0.000 0.330 4.039 Benzophenone 1.450 1.500 0.000 0.500 6.852 Benzyl alcohol 0.803 0.870 0.390 0.560 4.221 Benzyl Bromide 1.014 0.980 0.000 0.200 4.672 Benzyl chloride 0.821 0.860 0.000 0.140 4.353 Biphenyl 1.360 0.990 0.000 0.260 6.014 Bromobenzene 0.882 0.730 0.000 0.090 4.041 Butyric Acid 0.210 0.640 0.610 0.450 2.750 Butyronitrile 0.188 0.900 0.000 0.020 2.548 Caffeine 1.500 1.820 0.080 1.250 7.838 Chloroacetic acid 0.427 1.030 0.790 0.350 2.862 Chlorobenzene 0.718 0.650 0.000 0.070 3.657 Cyclohexane 0.310 1.000 0.000 0.000 2.964 Cyclohexanol 0.460 0.540 0.320 0.570 3.758 Diiodomethane 1.200 0.690 0.050 0.170 3.857 Diisopropylamine 0.053 0.210 0.070 0.740 2.893 Dimethyl Carbonate 0.142 0.540 0.000 0.570 2.328 Ethanol 0.246 0.420 0.370 0.480 1.485

52

Ethanolamine 0.458 0.670 0.520 0.900 2.432 Ethyl Acetate 0.106 0.620 0.000 0.450 2.314 Ethyl acetoacetate 0.208 0.800 0.000 0.860 3.752 Ethyl benzene 0.613 0.510 0.000 0.150 3.778 Ethyl benzoate 0.689 0.850 0.000 0.460 5.075 Ethyl decanoate 0.013 0.580 0.000 0.450 6.180 Ethyl glycol 0.404 0.900 0.580 0.780 2.661 Formamide 0.468 1.310 0.640 0.570 2.447 Formic Acid 0.343 0.750 0.760 0.330 1.545 Imidazole 0.710 0.850 0.420 0.780 4.018 Indole 1.200 1.120 0.440 0.220 5.505 Iodobenzene 1.188 0.820 0.000 0.120 4.502 Iso-pentyl acetate 0.051 0.570 0.000 0.470 3.740 Isoquinoline 1.211 1.000 0.000 0.540 5.595 L Menthol 0.400 0.500 0.230 0.580 5.177 Lactic acid 0.350 0.860 0.720 0.720 2.874 Malonic acid 0.380 1.460 0.990 0.590 3.616 Methyl Acetate 0.142 0.640 0.000 0.450 1.911 Methyl Benzoate 0.733 0.850 0.000 0.460 4.704 Methyl isobutyl ketone 0.111 0.650 0.000 0.510 3.089 Methyl-4-hydroxybenzoate 0.900 1.370 0.690 0.450 5.716 Morpholine 0.434 0.790 0.060 0.910 3.289 m-Toluic acid 0.730 0.890 0.600 0.400 4.819 N,N-Dimethyl acetamide 0.363 1.380 0.000 0.800 3.639 N,N-Diethyl aniline 0.953 0.800 0.000 0.410 5.287 N,N-Dimethyl aniline 0.957 0.810 0.000 0.410 4.701 N,N-Dimethylformamide 0.367 1.310 0.000 0.740 3.173 Naphthalene 1.340 0.920 0.000 0.200 5.161 Nitrobenzene 0.871 1.110 0.000 0.280 4.557 Nitromethane 0.313 0.950 0.060 0.310 1.892 Nonylamine 0.187 0.350 0.160 0.610 5.100 N,propyl alcohol 0.236 0.420 0.370 0.480 2.031 o-anisaldehyde 0.956 1.120 0.000 0.590 5.300 o-cresol 0.840 0.860 0.520 0.300 0.916 Octanoic acid 0.150 0.650 0.620 0.450 4.680 Octylamine 0.187 0.350 0.160 0.610 4.600 Pentan-1-ol 0.219 0.420 0.370 0.480 3.106 Phenanthrene 2.005 1.290 0.000 0.260 7.632 Phenol 0.805 0.890 0.600 0.300 3.766

53

Phenyl acetic Acid 0.730 1.080 0.660 0.570 4.962 Piperazine 0.570 0.850 0.300 1.140 3.438 Piperidine 0.422 0.400 0.060 0.770 3.075 Propanoic acid 0.233 0.650 0.610 0.440 2.276 Propionitrile 0.162 0.900 0.020 0.360 2.082 Propylene Carbonate 0.319 1.370 0.000 0.600 3.088 Pyrazine 0.629 0.820 0.000 0.640 2.875 Pyridine 0.631 0.840 0.000 0.520 3.022 Pyrrole 0.613 0.910 0.220 0.250 2.792 Quinoline 1.268 0.970 0.000 0.540 5.457 Resorcinol 0.980 1.110 1.090 0.520 4.618 Tetrachloroethylene 0.640 0.440 0.000 0.000 3.584 Tetrahydrofuran 0.289 0.520 0.000 0.480 2.636 Toluene 0.601 0.520 0.000 0.140 3.325 Triethylamine 0.101 0.150 0.000 0.790 3.040 Vanillin 1.028 1.280 0.330 0.680 5.730 Xanthene 1.502 1.070 0.000 0.230 7.153

The statistical software for social science (SPSS) were used to generate the log of

experimental data first, then the process coefficients (c, e, s, a, b, l) and R2 were obtained from

the experimental data using multiple linear regression analysis (MLRA) method. The process co-

efficient are used to acquire the log of retention time calculated (logtRcalc) as follow

Log = c + e.E+ s.S + a.A + b.B + l.L

ZB wax plus:

c=0.243, e= 0.043, s= 0.249, a= 0.242, b=0.008, l= 0.105, R2= 0.7005, F =51.391, SD

=0.0480 N= 84

Log (calculated) = 0.243 + 0.043E + 0.249S +0.242A + 0.008B + 0.105L (13)

ZB-35:

c= 0.250, e= 0.097, s= 0.075, a= 0.098, b= -0.027, l= 0.108, R2= 0.862, F = 113.177, SD=

0.037,

N= 85

Log (calculated) = 0.250 + 0.097E + 0.075S + 0.098A – 0.027B + 0.108 L (14)

54

TR1-MS:

c= 0.250, e=-0.043, s= 0.109, a= 0.105, b=-0.097, l=0.137, R2= 0.802, F=83.966, SD=

0.031,

N= 90

Log (calculated) = 0.250 – 0.043E + 0.109S + 0.105A – 0.097B + 0.137L (15)

TR-5:

c= 0.063, e=-0.032, s= 0.078, a= 0.160, b= -0.024, L =0.157, R2= 0.927, F =215.887,

SD= 0.023

N= 90

Log (calculated): 0.063- 0.032E +0.078S + 0.160A- 0.024B + 0.157L (16)

TG-5MS:

c= 0.151, e=0.066, s= 0.037, a=0.133, b=-0.021, l=0.129, R2= 0.873, F =122.144,

SD=0.038

N= 88

Log (calculated): 0.151 + 0.066E + 0.037S +0.133A - 0.021B + 0.129L (17)

TG-1301MS:

c=0.107, e= 0.030, s= 0.146, a= 0.167, b= 0.002, l= 0.134, R2= 0.816, F= 84.634,

SD=0.040

N= 82

Log (calculated) = 0.107 + 0.030E + 0.146S + 0.167 A + 0.002B + 0.134L (18)

R2 is the linear correlation coefficient square, F is the Fisher F-statistic, SD is the

standard deviation and N is the number of compounds

55

Here below are the experimental log and the calculated log of the six columns listed in

Tables 3.8 to 3.13.

Table 3.8. Experimental LogtR and LogtR calculated for column ZB wax plus Solute Log exp Log calc Solute Log exp Log calc 1-Bromohexane 0.786 0.792 Nonylamine 0.939 0.917 1,2-Dichlorobenzene 0.970 0.949 o-anisaldehyde 1.098 1.124 1,2-Dimethylbenzene 0.812 0.826 Octylamine* 0.895 0.865 2-Acetylpyridine 1.012 1.015 Phenyl acetic Acid 1.201 1.229

2-Butanone 0.593 0.669 Propylene Carbonate* 1.082 0.927

2-Chlorophenol* 1.084 1.017 Pyridine 0.810 0.801 2-Picoline 0.834 0.819 Quinoline 1.107 1.116 3-Amino-1-propanol* 0.985 0.891 Tetrachloroethylene 0.680 0.756 Acetamide 1.055 1.039 Tetrahydrofuran* 0.540 0.666 Acetic Acid* 0.960 0.758 Toluene 0.695 0.749 Acetone* 0.504 0.617 1-Butanol 0.745 0.724 Acetophenone 1.027 1.006 1-Octanol* 0.971 0.918 Alpha pinene 0.683 0.750 2-Butoxyethanol* 0.909 0.835

Amyl acetate 0.800 0.803 2-Methyl -2-Pentanol 0.708 0.745

Aniline* 1.056 1.002 4-Chlorophenol 1.186 1.216 Benzene* 0.603 0.692 4-Methyl-2 pentanol 0.764 0.759 Benzoic Acid* 1.197 1.133 4-Nitrotoluene 1.075 1.100 Benzonitrile 1.013 0.978 Acetic anhydride* 0.820 0.762 Benzyl chloride 0.979 0.951 Benzyl bromide 1.005 1.023 Biphenyl 1.103 1.182 Butyric acid* 0.987 0.851 Bromobenzene 0.906 0.888 Butyronitrile 0.710 0.746 Chlorobenzene 0.830 0.820 Cyclohexane 0.525 0.592 Diiodomethane 0.848 0.885 Cyclohexanol 0.912 0.874 Ethanol 0.599 0.607 Diisopropylamine* 0.515 0.624 Ethyl Acetate* 0.555 0.649 Dimethyl carbonate 0.606 0.633 Ethyl benzoate 1.031 1.021 Ethanolamine* 0.906 0.818 Ethyl decanoate 1.017 1.040 Ethyl Acetoacetate* 0.934 0.852 Formamide 1.004 1.006 Ethylbenzene 0.732 0.794 Isoquinoline 1.117 1.136 Ethylene glycol* 1.003 0.910 Lactic acid* 0.887 0.954 Formic acid* 0.524 0.793 Mesitylene 0.850 0.858 Iodobenzene 0.961 0.972 Methyl acetate* 0.512 0.613 Malonic acid* 0.926 1.247 Methyl benzoate 1.017 0.984 N,N 0.916 0.991

56

dimethylacetamide* Methyl isobutyl ketone 0.664 0.738 Nitromethane* 1.075 0.709 Methyl cyclohexane* 0.888 0.617 Octanoic acid* 1.111 1.056 Morpholine 0.852 0.826 Piperidine 0.671 0.704 N,propyl alcohol 0.591 0.664 Propionitrile 0.642 0.700 N,N-Diethylaniline 1.016 1.042 Pyrrole* 0.958 0.844 N,N-Dimethylaniline 0.992 0.983 Triethyl amine* 0.518 0.610 N,N-Dimethylformamide 0.899 0.924 Pentan-1-ol* 0.848 0.777 Naphthalene 1.055 1.073 Phenol* 1.125 1.042 Nitrobenzene 1.054 1.038 1-Bromopropane* 0.461 0.609 1-Nonene* 0.543 0.652 1-Octene* 0.417 0.601 2- Propanol 0.534 0.605 Propanoic Acid* 0.959 0.803

*(asterisk) signifies compounds that are outliers and are not used for the least square method.

Table 3.9. Experimental LogtR and LogtR calculated for column ZB 35 Solute Log exp Log calc Solute Log exp Log calc 1,3,5-Trimethylbenzene 0.840 0.809 Octylamine* 0.875 0.792 1-Bromohexane* 0.810 0.748 Pentane-1-ol 0.660 0.655 1 -Chloronaphthalene 1.070 1.092 Phenol 0.873 0.849 1-Nitronaphthalene* 1.145 1.291 Phenylacetic Acid 1.016 0.994 1,2-Dichlorobenzene 0.908 0.873 Pyridine 0.689 0.683 1,2-Dimethylbenzene 0.791 0.769 Quinoline 1.027 1.027 2-Acetylpyridine 0.921 0.869 Resorcinol 1.036 1.025 2-Butanone 0.529 0.545 Tetrachloroethylene 0.702 0.719 2-Chlorobenzoic acid* 1.062 0.989 Toluene 0.675 0.691 2-Chlorophenol 0.880 0.871 Vanillin 1.084 1.092 2-Picoline 0.749 0.717 1-Butanol* 0.499 0.599 4-Nitrophenol* 1.119 1.201 1,2-Dibromoethane* 0.698 0.741 Acenaphthene* 1.104 1.182 1-Bromopropane* 0.453 0.580 Acetanilide 1.080 1.076 1-Nonene 0.686 0.691 Acetic Acid 0.536 0.559 1-Octanol 0.880 0.823 Acetone 0.472 0.484 1-Octene* 0.571 0.634 Acetophenone* 0.941 0.881 2 Propanol* 0.367 0.495 Alpha pinene 0.788 0.755 2-Butoxyethanol* 0.773 0.710

Amyl acetate* 0.795 0.702 2-Methyl -2-Pentanol* 0.558 0.648

Aniline 0.893 0.853 2 - Methyl -2 propanol* 0.384 0.507

Aspirin* 1.000 1.201 4-Chlorophenol 0.987 0.996

57

Benzene* 0.576 0.632 4-Methyl-2 pentanol 0.635 0.656 Benzoic Acid 0.979 0.940 4-Nitrotoluene 0.994 0.969 Benzonitrile* 0.900 0.832 Acetic anhydride 0.616 0.610 Benzophenone* 1.144 1.245 Benzyl alcohol 0.900 0.874 Benzyl chloride 0.902 0.856 Benzyl bromide 0.936 0.919 Biphenyl* 1.066 1.102 Butyric acid* 0.607 0.657 Chlorobenzene 0.758 0.751 Butyronitrile 0.609 0.594 Ethanol 0.452 0.476 Cyclohexane* 0.459 0.590 Ethyl Acetate 0.528 0.536 Cyclohexanol 0.763 0.755 Ethyl benzoate 0.979 0.920 Diisopropylamine* 0.503 0.566 Ethyl decanoate* 1.034 0.957 Dimethyl carbonate* 0.474 0.533 Formamide* 0.825 0.705 Ethanolamine* 0.583 0.634 Isopentyl acetate* 0.762 0.686 Ethylbenzene 0.750 0.742 Isoquinoline 1.035 1.039 Iodobenzene 0.897 0.904 Lactic acid* 0.656 0.711 Ethylene glycol* 0.602 0.681 Methyl Acetate 0.479 0.496 L-menthol 0.938 0.896

Methyl isobutyl ketone 0.644 0.625 N,N- dimethyl acetamide 0.796 0.769

Methyl-4-hydroxybenzoate 1.093 1.123 Nitromethane* 0.456 0.543 Morpholine 0.734 0.692 Octanoic acid 0.908 0.869 m, Toluic acid* 1.018 0.958 Piperidine 0.651 0.636 N,N-Diethylaniline 0.997 0.965 Propanoic Acid 0.607 0.607 Naphthalene 0.994 1.000 Propionitrile* 0.462 0.542 Nitrobenzene 0.957 0.902 Pyrazine 0.632 0.663 Nonylamine* 0.931 0.848 Pyrrole* 0.650 0.686 o-anisaldehyde* 1.051 0.991 Triethyl amine* 0.522 0.575 o-cresol* 0.920 0.522

*(asterisk) signifies compounds that are outliers and are not used for the least square method.

Table 3.10. Experimental LogtR and LogtR calculated for column TR-1MS Solute Log exp Log calc Solute Log exp Log calc 1,3,5-Trimethylbenzene 0.936 0.875 n-Propyl alcohol 0.611 0.579 1-bromohexane 0.905 0.855 o-anisaldehyde* 1.078 0.994 1 -chloronaphthalene 1.099 1.096 Octylamine* 0.967 0.874 1-nitronaphthalene* 1.154 1.281 Pentane-1-ol 0.781 0.720 1,2-Dichlorobenzene 0.961 0.932 Phenanthrene* 1.195 1.320 2-acetylpyridine* 0.954 0.880 Phenol* 0.928 0.874 2-butanone 0.651 0.598 Phenyl acetic Acid 1.049 1.023 2-chlorophenol 0.939 0.896 Pyridine 0.758 0.690 2-picoline 0.818 0.728 Quinoline 1.048 0.997

58

acenaphthene 1.128 1.165 Resorcinol 1.056 1.023 Acetanilide 1.089 1.084 Tetrachloroethylene 0.823 0.792 Acetic Acid 0.667 0.600 Toluene 0.785 0.749 Acetone 0.626 0.527 Vanillin 1.097 1.084 Acetophenone* 0.975 0.897 Xanthene 1.168 1.258 Alpha pinene* 0.922 0.852 1-Butanol* 0.514 0.654 Amyl acetate* 0.889 0.804 1-octanol 0.893 0.919 Aniline* 0.924 0.849 2-butoxyethanol 0.772 0.748

Benzene 0.701 0.678 2-Methyl -2-Pentanol* 0.593 0.703

Benzoic Acid 1.021 0.981 2 - Methyl -2 propanol* 0.398 0.540

Benzonitrile* 0.925 0.867 4-Chlorophenol* 0.955 1.039

Benzophenone 1.159 1.225 4-Methyl-2 pentanol* 0.620 0.722

Benzyl chloride 0.949 0.907 4-Nitrotoluene 0.964 1.015 Biphenyl 1.096 1.103 Acetic anhydride* 0.399 0.646 Chlorobenzene* 0.911 0.809 Benzyl bromide 0.905 0.945 Ethanol 0.595 0.507 Butyric acid 0.720 0.722 Ethyl Acetate 0.661 0.604 Butyronitrile* 0.500 0.668 Ethyl benzoate 1.021 0.965 Cyclohexane* 0.521 0.692 Ethyl decanoate 1.097 1.110 Cyclohexanol 0.750 0.792 Formamide* 0.823 0.721 Diisopropylamine* 0.515 0.617

Isopentyl acetate* 0.870 0.786 Dimethyl carbonate* 0.457 0.583

Isoquinoline 1.057 1.020 Ethanolamine 0.524 0.610 Lactic acid* 0.889 0.731 Ethyl Acetoacetate 0.786 0.754 Methyl Acetate 0.628 0.552 Ethylbenzene 0.734 0.806 Methyl isobutyl ketone 0.756 0.700 Iodobenzene 0.871 0.913 Methyl-4-hydroxybenzoate 1.110 1.160 Ethylene glycol* 0.567 0.683

Morpholine* 0.798 0.685 N,N- dimethylacetamide 0.719 0.793

N,N-Diethylaniline 1.044 0.986 Octanoic acid 0.923 0.978 N,N dimethylaniline* 0.987 0.910 Piperidine 0.621 0.641 Naphthalene 1.034 0.993 Propionitrile* 0.415 0.609 Nitrobenzene 0.984 0.936 Pyrrole* 0.605 0.722 Nonylamine* 1.014 0.939 Triethylamine 0.546 0.616

*(asterisk) signifies compounds that are outliers and are not used for the least square method.

59

Table 3.11. Experimental LogtR and LogtR calculated for column TR-5 Solute Log exp Log calc Solute Log exp Log calc

1,3, 5-Trimethylbenzene 0.812 0.741 N,N- dimethylaniline* 0.897 0.795

1-Bromohexane 0.786 0.718 Naphthalene* 0.949 0.857 1 -Chloronaphthalene 1.032 0.969 Nitrobenzene* 0.900 0.804 1-Nitronaphthalene* 1.099 1.189 Nonylamine 0.925 0.890 1,2-Dichlorobenzene* 0.863 0.778 n-Propyl alcohol* 0.379 0.448 1,2-Dimethylbenzene 0.749 0.680 o-anisaldehyde 0.974 0.909 2-Acetylpyridine 0.861 0.783 Octylamine 0.863 0.812 2-Butanone 0.424 0.454 Pentan-1-ol 0.609 0.618 2-Chlorobenzoic acid 1.026 0.949 Phenanthrene* 1.144 1.231 2-Chlorophenol 0.830 0.778 Phenol 0.821 0.763 2-Picoline 0.663 0.608 Phenylacetic Acid 0.973 0.973 3-Amino-1-propanol 0.687 0.612 Pyridine 0.579 0.551 3-Nitrobenzoic acid 1.089 1.063 Quinoline 0.975 0.904 Acenaphthene 1.065 1.056 Resorcinol 0.986 0.976 Acetanilide* 1.026 1.036 Tetrachloroethylene 0.660 0.620 Acetic Acid 0.458 0.470 Toluene 0.603 0.585 Acetone 0.370 0.367 Vanillin 1.034 1.035 Acetophenone* 0.885 0.786 Xanthene* 1.113 1.171 Alpha pinene 0.788 0.720 1-Butanol* 0.421 0.538 Amyl acetate 0.764 0.698 1.2 dibromoethane 0.637 0.619 Aniline* 0.820 0.728 1-Bromopropane* 0.433 0.480 Benzoic Acid 0.960 0.904 1-Nonene 0.728 0.701 Benzonitrile* 0.825 0.730 1-octene 0.614 0.622 Benzophenone* 1.104 1.154 2 propanol* 0.352 0.394 Benzyl chloride* 0.845 0.759 4-chlorophenol* 0.923 0.943

Biphenyl 1.029 0.994 4-Methyl-2 pentanol* 0.545 0.630

Chlorobenzene 0.700 0.642 Benzyl alcohol 0.854 0.793 Ethanol 0.358 0.361 Butyronitrile* 0.435 0.513 Ethyl Acetate 0.433 0.457 Cyclohexane* 0.416 0.517 Ethyl benzoate 0.941 0.872 Cyclohexanol* 0.697 0.704 Ethyl decanoate* 1.029 1.067 Diisopropylamine* 0.414 0.524 Formamide* 0.695 0.609 Ethylbenzene 0.665 0.654 Isopentyl acetate 0.732 0.680 Iodobenzene 0.831 0.757 Isoquinoline 0.985 0.931 L-menthol 0.931 0.913 Lactic acid* 0.773 0.658 Nitromethane* 0.337 0.417 Methyl Acetate 0.383 0.393 Piperidine 0.541 0.542

60

Methyl isobutyl ketone 0.573 0.580 Propanoic Acid 0.584 0.544 Methyl-4-hydroxybenzoate* 1.050 1.111 Propionitrile* 0.343 0.445 Morpholine 0.652 0.602 Pyrrole 0.547 0.564 N,N-Diethylaniline 0.966 0.887 Triethylamine* 0.443 0.527

*(asterisk) signifies compounds that are outliers and are not used for the least square method.

Table 3.12. Experimental LogtR and LogtR calculated for column TG-5MS Solute Log exp Log calc Solute Log exp Log calc 1,3, 5-Trimethylbenzene 0.806 0.769 Nonylamine* 0.920 0.843 1-Bromohexane* 0.777 0.719 n-Propyl alcohol* 0.347 0.483 1-Nitronaphthalene* 1.097 1.220 o-anisaldehyde* 1.007 0.927 1,2-Dichlorobenzene 0.859 0.819 o-cresol* 0.868 0.419 1,2-Dimethylbenzene 0.739 0.720 Octylamine* 0.859 0.778 2-Acetylpyridine 0.855 0.797 Pentan-1-ol 0.595 0.621 2-Butanone 0.413 0.472 Phenanthrene* 1.141 1.310 2-Chlorobenzoic acid* 1.020 0.950 Phenol 0.814 0.796 2-Chlorophenol 0.825 0.815 Phenyl acetic Acid 0.975 0.955 2-Picoline 0.649 0.647 Pyridine 0.568 0.603 3-Amino-1-propanol 0.680 0.633 Quinoline 0.972 0.963 3-Nitrobenzoic acid 1.085 1.058 Resorcinol 0.981 0.987 4-Nitrophenol 1.070 1.147 Tetrachloroethylene 0.651 0.672 Acenaphthene 1.063 1.126 Toluene 0.599 0.636 Acetanilide 1.023 1.019 Vanillin 1.031 1.035 Acetic Acid* 0.429 0.500 1-Butanol* 0.484 0.556 Acetone 0.347 0.403 1,2 dibromoethane 0.637 0.674 Acetophenone 0.880 0.813 1-Bromopropane* 0.433 0.525 Amyl acetate* 0.757 0.664 1-Nonene 0.728 0.684 Aniline 0.816 0.783 1-Octene 0.614 0.619 Aspirin* 0.997 1.155 2 Propanol* 0.352 0.438 Benzene* 0.475 0.567 2-Butoxyethanol* 0.757 0.673

Benzoic Acid 0.956 0.903 2-Methyl -2-Pentanol* 0.564 0.619

Benzonitrile* 0.822 0.755 2 - Methyl -2 propanol* 0.370 0.456

Benzophenone 1.101 1.176 4-Chlorophenol 0.949 0.952

Benzyl chloride 0.843 0.796 4-Methyl-2 pentanol 0.599 0.627

Biphenyl 1.027 1.048 Benzyl alcohol 0.854 0.821 Chlorobenzene 0.690 0.693 Benzyl bromide 0.901 0.853 Ethanol 0.333 0.413 Butyronitrile 0.492 0.518

61

Ethyl Acetate 0.423 0.470 Cyclohexane* 0.479 0.558 Ethyl benzoate* 0.937 0.873 Cyclohexanol 0.741 0.717 Ethyl decanoate 1.026 0.961 Diisopropylamine 0.476 0.529 Formamide* 0.711 0.619 Dimethyl carbonate 0.434 0.469 Isopentyl acetate* 0.721 0.648 Ethanolamine* 0.497 0.570 Isoquinoline 0.982 0.978 Ethyl benzene 0.715 0.695 Lactic acid* 0.593 0.657 Iodobenzene 0.866 0.838 Methyl Acetate 0.362 0.421 L-menthol 0.931 0.882

Methyl isobutyl ketone 0.564 0.570 N,N- dimethylacetamide 0.720 0.679

Methyl-4-hydroxybenzoate 1.046 1.081 Nitromethane 0.392 0.452 Morpholine 0.628 0.622 Piperidine 0.596 0.582 N,N-Diethylaniline 0.962 0.917 Propanoic Acid 0.584 0.556 N,N dimethylaniline 0.894 0.842 Propionitrile 0.403 0.459 Naphthalene 0.946 0.935 Pyrrole 0.591 0.609 Nitrobenzene 0.894 0.832 Triethylamine 0.505 0.539

*(asterisk) signifies compounds that are outliers and are not used for the least square method

Table 3.13. Experimental LogtR and LogtR calculated for column TG-1301MS Solute Log exp Log calc Solute Log exp Log calc 1,3,5-Trimethylbenzene 0.818 0.781 Phenol 0.901 0.863 1-Bromohexane* 0.795 0.724 Pyridine 0.618 0.658 1-Chloronaphthalene 1.048 1.076 Quinoline 0.998 1.015 1,2-Dichlorobenzene 0.879 0.850 Tetrachloroethylene 0.658 0.671 1,2-Dimethylbenzene 0.757 0.735 Toluene 0.619 0.648 2-Acetylpyridine 0.888 0.879 1-Butanol 0.543 0.585 2-Butanone 0.462 0.525 1,2-Dibromoethane 0.679 0.713 2-Chlorophenol 0.873 0.872 1-Bromopropane 0.442 0.531 2-Picoline 0.688 0.695 1-Nonene* 0.727 0.659 3-Amino-1-propanol 0.758 0.714 1-Octanol 0.906 0.843 Acenaphthene* 1.079 1.170 1-Octene 0.615 0.594 Acetic Acid 0.535 0.558 2 Propanol* 0.370 0.463 Acetophenone 0.916 0.880 2-Butoxyethanol* 0.791 0.719

Alpha pinene* 0.777 0.712 2-Methyl -2-Pentanol 0.611 0.638

Amyl acetate* 0.786 0.705 2 - Methyl -2 propanol 0.397 0.475

Aniline 0.869 0.847 4-Chlorophenol* 0.792 1.035

Benzene* 0.503 0.580 4-Methyl-2 pentanol 0.649 0.648

62

Benzoic Acid 1.003 0.974 4-Nitrotoluene 0.989 0.980 Benzonitrile 0.871 0.832 Acetic anhydride 0.629 0.610 Benzyl chloride 0.870 0.839 Benzyl alcohol 0.904 0.885 Biphenyl 1.043 1.093 Benzyl bromide 0.919 0.905 Chlorobenzene 0.714 0.715 Butyric acid* 0.757 0.674 Ethanol 0.373 0.443 Butyronitrile 0.567 0.588 Ethyl Acetate 0.463 0.514 Cyclohexane 0.470 0.529 Ethyl benzoate 0.960 0.925 Cyclohexanol 0.781 0.753 Ethyl decanoate 1.039 0.999 Diisopropylamine 0.478 0.538 Formamide* 0.805 0.749 Ethanolamine 0.587 0.634

Isoquinoline 1.011 1.035 Ethyl Acetoacetate* 0.827 0.729

Lactic acid* 0.654 0.746 Ethylbenzene 0.721 0.705 Methyl isobutyl ketone 0.616 0.618 Ethylene glycol 0.664 0.704 Morpholine 0.691 0.687 Iodobenzene 0.877 0.867 N,N-Diethylaniline 0.981 0.955 L-menthol 0.955 0.912 N,N- dimethylaniline 0.916 0.882 Malonic acid 0.930 0.972

Naphthalene 0.969 0.972 N,N- dimethylacetamide 0.793 0.806

Nitrobenzene 0.932 0.904 Nitromethane 0.456 0.526 Nonylamine* 0.931 0.860 Octanoic acid 0.979 0.922 n-Propyl alcohol* 0.392 0.513 Piperidine 0.608 0.602 o-anisaldehyde 1.028 1.004 Propanoic Acid 0.659 0.616 o-cresol* 0.930 0.483 Propionitrile 0.463 0.530 Octylamine* 0.871 0.796 Pyrrole 0.681 0.673 Pentan-1-ol 0.661 0.650 Triethylamine 0.502 0.539

*(asterisk) signifies compounds that are outliers and are not used for the least square method

Shown below are the linear correlation between the LogtR (experimental) and LogtR

(calculated) for the six columns used in Figure 3.1

63

y = 0.9883xR² = 0.7144

N = 92

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

(cal

cula

ted)

log (experiemental)

ZB Wax Plus

a

y = 0.9931xR² = 0.8646

N = 94

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

(cal

cula

ted)

log (experimental)

ZB 35

b

64

y = 0.9894xR² = 0.8021

N = 90

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

(cal

cula

ted)

log (experimental)

TR1 MS

c

y = 0.9705xR² = 0.9272

N = 80

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

(cal

cula

ted)

log (experimental)

TR 5

d

65

Figure 3.1. Correlation of LogtR (calculated) and LogtR (experimentally) observed for the six

columns. ZB wax plus (a), ZB 35(b), TR-1MS(c), TR-5(d), TG-5MS (e), TG-1301MS (f)

y = 0.9913xR² = 0.8725

N = 88

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

(cal

cula

ted)

log (experimental)

TG5 MS

e

y = 0.9866xR² = 0.8162

N = 82

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

calc

ulat

ed

log experimental

TG1301 MS

f

66

3.2 Discussion

3.2.1 Active Compounds for Each Column

After analysis of the data, the least square method was applied to characterize the

correlation between the LogtR (calculated) and the LogtR (experimental) in this study. Not all

data fit on the trend line, thus the outliers were removed by using the standard error bar for each

points. Table 3.8.1 to table 3.8.6 shows all effective or active compounds and all outliers that

were removed. The correlation coefficient of LogtR (calculated) and LogtR (experimental) got

better or increase close to 1 which indicated a better correlation between data when outliers are

removed. Below are the correlations between the experimental and calculated log for all six

columns with no outliers.

y = 1.0073xR² = 0.9605

N = 59

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

(cal

cula

ted)

log (experimental)

ZB Wax Plus

a

67

y = 0.9836xR² = 0.9815

N = 55

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

(cal

cula

ted)

log (experimental)

ZB 35

b

y = 0.958xR² = 0.9509

N = 39

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

(cal

cula

ted)

log (experimental)

TR1 MS

c

68

y = 0.9517xR² = 0.9772

N = 50

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

(cal

cula

ted)

log (experimental)

TR5

d

y = 0.9935xR² = 0.9608

N = 62

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

(cal

cula

ted)

log (experimental)

TG5 MS

e

69

Figure 3.2. Correlation of LogtR (calculated) and LogtR (experimentally) observed for the six

columns ZB wax plus (a), ZB 35(b), TR- 1MS(c), TR-5(d), TG-5MS (e), TG1301 MS (f) for just active compounds.

After the removal of the outliers, the linear coefficients (R2) of the six columns increased.

The R2 now lies between 0.95 and 0.98 which is close to 1 meaning that the experimental and

calculated values of active compounds have a good correlation. The six columns used have

different polarities; from non-polar, mid or low polarity to a polar stationary phase. Depending

on the type of organic compounds used, not all samples would interaction very well on each

stationary phase. Some organic compounds would interact better with one stationary phase than

the other. We do not anticipate all compounds to interact due to the difference of the stationary

phase of all six columns. The rule of like dissolves like is convenient, compounds that are non-

polar would interact very well with non-polar stationary phase and polar compounds would do

the same with polar stationary phase. The mid and low polarity stationary phase can interact well

y = 0.9969xR² = 0.9515

N = 65

0.0

0.5

1.0

1.5

0.0 0.5 1.0 1.5

log

(cal

cula

ted)

log (experimental)

TG1301 MS

f

70

with polar and non- polar organic compounds depending on their boiling point and how strong

they interact with the stationary phase.

The removal of ineffective compounds or outliers allows the recalculation of new process

coefficient with only the active or effective compounds.

With the new process coefficients, a new set of Abraham solvation model equations are

established

ZB wax plus:

c= 0.177, e= 0.036, s= 0.284, a= 0.272, b= 0.007, l= 0.112, R2 = 0.961, SD= 0.013,

F=377.789

N= 59

Log (calculated) = 0.177 + 0.036E + 0.284S + 0.272A + 0.07B + 0.112L (19)

ZB 35:

c=0.191, e=0.061, s=0.087, a=0.082, b=-0.003, l=0.127, R2= 0.982, SD=0.010, F=

682.767

N=55

Log (calculated) = 0.191 + 0.061E + 0.087S + 0.082A – 0.003B + 0.127 (20)

TR1 MS:

c=0.361, e=-0.048, s= 0.131, a= 0.086, b= -0.133, l= 0.121, R2= 0.951, SD= 0.017, F=

172.851

N=39

Log (calculated) =0.361 – 0.048E + 0.131S +0.086A – 0.133B + 0.121L (21)

TR-5:

c=0.055, e=-0.047, s= 0.064, a= 0.146, b= -0.014, l =0.161, R2= 0.977, SD= 0.018, F=

445.857

N=50

71

Log (calculated) = 0.055 – 0.047E + 0.064S +0.146A – 0.014B + 0.161L (22)

TG-5 MS:

c=0.106, e= 0.057, s= 0.011, a= 0.129, b=-0.010, l=0.146, R2= 0.961, SD=0.015, F=

377.789

N=62

Log (calculated) = 0.106 + 0.057E + 0.011S + 0.129A – 0.010B + 0.146L (23)

TG1301 MS:

c=0.028, e=0.007, s=0.155, a=0.184, b= 0.009, l=0.154, R2= 0.952, SD= 0.014, F=

422.273

N=65

Log (calculated) = 0.028+ 0.007E +0.155S + 0.184A + 0.009B + 0.154L (24)

3.2.2 Data Interpretation

The coefficients e, s, a, b, l and v are not just curve- fitting constants. The process

coefficients reflect specific solute-solvent interactions that correspond to chemical properties of

the solvent phase. They represent the stationary phase contribution to intermolecular interaction.

The process coefficient or regression coefficients are very important, because they will encode

stationary phase properties. The coefficient can be considered as constants that characterized the

stationary phase. The gas phase will be the reference for such characterization because all gas

chromatography data refers to transfer from the gas phase to the stationary phase. Therefore the

process coefficient does not just represent a new method for characterization of stationary phase,

but they also contain chemical information about the stationary phase. The process coefficients

are the average value over the range of temperatures. The interpretation of the regression

constants are as follows. The e-coefficient will determine the phase interaction with solutes

through π-and n- electrons pairs. Usually the e coefficient is positive, but for phase that contains

72

strong electronegativity such as fluorine, the e can be negative. The s coefficient shows the

tendency of the phase to interact with dipolar or polarizable solutes. The a coefficient indicates

the hydrogen bond basicity of the phase because acidic solute will interact with a basic phase and

the b coefficient measure the hydrogen- bond acidity of the phase. The l co-efficient is a measure

of size needed to form solvent cavity and dispersion forces. Thus we expected the l values to

increase as the size of molecule increases [54, 55]. The ZB wax plus (polyethylene glycol or

PEG) column is the most polar and acidic among the six columns. The process coefficient s

(=0.284) and a (=0.272) for ZB wax plus columns are the highest compared to the other columns

which is a good prediction because of the polarity of ZB wax plus column. In reference to table

1.3 above, the PEG functional group has a strong dipole and moderate hydrogen bonding. Since

TG 1301 MS column is one of the mid polar column among the six columns used, the process

coefficient s (=0.155) and a (=0.184) are the second highest after the ZB wax plus column

because of the cyano functional group in the stationary phase. In reference to table 1.3, it’s

shown that the cyano functional group has a strong dipole interaction and moderate hydrogen

bonding. The remaining columns, ZB 35, TR-5, TG 5-MS and TR 1-MS have mid polarity, low

polarity and non-polar stationary phase with methyl and phenyl group. The stationary phase

interactions in reference to Tale 1.3 indicate that methyl and phenyl group has none to weak

dipole and none to weak hydrogen bonding. The process coefficients s and a value for those four

columns are lower compared to ZB wax and TG1301MS. It is significant to note that the s, a,

and b processes for gas- phase must be positive or close to zero because interactions between the

phase and the solute will increase the solubility of a gaseous solute. The process coefficients s, a,

and b for ZB wax plus(s=0.284, a=0.272, b= 0.007) and TG 1301 MS(s=0.155, a= 0.184, b=

0.009) are all positive. The regression coefficients s, a, and b for ZB 35(s= 0.087, a= 0.082. b=-

73

0.003), TG5-MS(s=0.011, a= 0.129, b = -0.01), TR 5(s= 0.064, a= 0.146. b= -0.014), TR1

MS(s= 0.131, a = 0.086, b=-0.133) are positive except for the basicity which is close to zero. TR

1 MS has an exception by having a high negative value of b coefficients. If more compounds are

added, the process coefficients can be recalculated and thus produce new stationary equations.

Most stationary phases in gas chromatography do not have a strong hydrogen bonding; therefore

the basicity and B descriptors are not suitable to be determined by gas chromatography. In

general the constants s, a, b, l all decrease with increase in temperature [7, 55].

3.2.3 Molecular Descriptors

Drugs studied are nicotine, methamphetamine, oxycodone, ketamine, and heroin.

Molecular descriptors for those drugs are calculated by converting average retention time

into calculated log of retention time (LogtR calculated). The LogtR calculated are compared with

the experimental determined values. Microsoft solver is used to minimize the sum of squares on

the set of describes system equations. The systems equations contains known process

coefficients (e, s, a, b, l or v) which are determined by multiple linear regression analysis

(MLRA) method. The sums of squares are set at a minimum to fit the targeted cell S, A, B and L

[56]. Gas chromatography was used to measure the drugs retention time. Table3.8. show the

retention time of illicit drugs and Table 3.8.8 show a summary of coefficients for GC stationary

phases.

Table 3.14. Retention time (min) of illicit drugs Illicit drug Column Run1 Run2 Run3 Avg Stdev %RSD

Ketamine

ZB Wax 17.747 17.758 17.762 17.756 0.008 0.044 ZB 35 15.465 15.463 15.463 15.464 0.001 0.007 TR 1 MS 14.248 14.253 14.253 14.251 0.003 0.020 TR 5 14.208 14.213 14.218 14.213 0.005 0.035 TG 5 MS 14.613 14.615 14.612 14.613 0.002 0.010 TG 1301 MS 14.945 14.957 14.952 14.951 0.006 0.040

74

Heroin

ZB 35 22.137 22.128 22.143 22.136 0.008 0.034 TR 1 MS 18.972 18.970 18.972 18.971 0.001 0.006 TR 5 19.075 19.057 19.058 19.063 0.010 0.053 TG 5 MS 19.722 19.725 19.700 19.716 0.014 0.069 TG 1301 MS 20.888 20.920 20.915 20.908 0.017 0.082

Methamphetamine

ZB Wax 11.968 11.965 11.965 11.966 0.002 0.014 TR 1 MS 5.585 5.585 5.563 5.578 0.013 0.228 TR 5 7.120 7.118 7.118 7.119 0.001 0.016 TG 5 MS 6.148 6.148 6.158 6.151 0.006 0.094 TG 1301 MS 12.618 12.618 12.623 12.620 0.003 0.023

Oxycodone TG 5 MS 11.682 11.698 11.682 11.687 0.009 0.079 Nicotine ZB Wax 11.897 11.898 11.900 11.898 0.002 0.013

Table 3.15. Process coefficients for GC stationary phases Column c e s a b l v ZB Wax Plus 0.177 0.036 0.284 0.272 0.007 0.112 0.000 ZB 35 0.191 0.061 0.087 0.082 -0.003 0.127 0.000 TR1 MS 0.361 -0.048 0.131 0.086 -0.133 0.121 0.000 TR5 0.055 -0.047 0.064 0.146 -0.014 0.161 0.000 TG5 MS 0.106 0.057 0.011 0.129 -0.010 0.146 0.000 TG1301 MS 0.028 0.007 0.155 0.184 0.009 0.154 0.000 Octanol/water 0.088 0.562 -1.054 0.034 -3.460 0.000 3.814

Not all illicit drugs ran on all six columns. The results show the run of each drug on each

column they did elute. The excess molar refraction and the McGowan volume V, were found

from the literature [50-52]. Since there are few data points for the illicit drugs, a very good

correlation is not expected therefore the introduction of octanol/water partition coefficient is

added to the data set. The log of P (octanol/water) can be found in literature. The log of P is a

condense to condense phase, thus the McGowan volume needs to be added. The Abraham model

equation for octanol/water is represented as:

Octanol/water, c= 0.088, e=0.562, s= -1.054, a= 0.034, b=-3.460, v= 3.814

LogP(calculated) = 0.088 + 0.562E – 1.054S + 0.034A -3.460B + 3.814V (25)

75

The log of P (eq.25) is combined with the previous six stationary equation (eq.19 to

eq.24) to predict the solute descriptors for illicit drugs.

3.2.3.1 Nicotine

Calculated log of retention time is determine through equation 19 to equation 25 (Table

3.9.1)

Table 3.16. Observed and calculated retention data for nicotine Stationary phase Experimental LogtR Calculated LogtR ZB wax plus 1.075 1.075 Octanol/water 1.170 1.170

The literature solute descriptors for Nicotine are: E= 0.865, S= 0.880, A= 0.000. B=

1.090, L= 5.880, V= 1.371[ref.62]

Table 3.17. Predicted solute descriptors for nicotine Descriptors E S A B L V Values 0.865 0.870 0.000 1.073 5.880 1.371

The solute descriptors in bold are the calculated one. The remaining descriptors obtained

from the literature were kept constant. The standard deviation for the predicted solutes

descriptors for nicotine is 6.23*10-8 log unit. Nicotine did run only on ZB wax plus column; thus

only two stationary equations are represented. The two data set is not enough to conclude. The

calculated A descriptor is 0.000; there is no acidic characteristic in nicotine. Overall nicotine is

considered as a weak base because of the two nitrogen, its B descriptor is 1.073 which displays

basic tendency. Nicotine does also show sign of polarity with the S descriptor of 0.870. Tobacco

is a plant grown for its leaves, which are smoke, chewed for a variety of effects. Nicotine is

contained in tobacco, it’s an addictive substance.

76

N

N

CH3

H

Figure 3.3. Structure of nicotine

3.2.3.2 Oxycodone

Calculated log of retention time is determined through equation 19 to equation 25(Table

3.9.3)

Table 3.18. Observed and calculated retention data for oxycodone Stationary phase Experimental LogtR Calculated LogtR TG 5MS 1.067 1.068 Octanol/water 1.260 1.260

The literature solute descriptors for oxycodone are E= 2.015, S= 2.815, A= 0.286, B=

2.228, V= 2.264

Table 3.19. Predicted solute descriptors for oxycodone Descriptors E S A B L V Values 2.015 2.564 0.286 1.706 5.471 2.264

The solute descriptors in bold are the calculated one. The overall standard deviation for

the predicted solutes descriptors for oxycodone is 8.12*10-7 log unit. The oxycodone did run

only on TG5MS column (5% diphenyl 95% dimethyl polysiloxane). Since there are few data

sets, a good conclusion cannot be made. The oxycodone( Figure 3.4) structure has one hydrogen

that exhibit the acidic characteristic, thus the A descriptor is 0.286. overall the drug is basic

because of the amine group. The nitrogen( strong electronegativity element) also gives the

polarizability characteristic of the drug with S = 2.564, the hydroxide group create a strong base

group with the B value = 1.706. Oxycodone is an opioid, use to treat moderate to severe pain.

77

Figure 3.4. Structure of oxycodone

3.2.3.3 Methamphetamine

Calculated log of retention time is determined through equation 19 to equation 25(Table

3.9.5)

Table 3.20. Observed and calculated retention data for methamphetamine Stationary phase Experimental LogtR Calculated LogtR ZB was plus 1.077 1.130 ZB 35 --- --- TR1MS 0.746 0.798 TR5 0.852 0.854 TG5MS 0.788 0.877 TG1301MS 1.101 0.935 Octanol/water 0.207 0.206

The literature solute descriptors for methamphetamine are Ea= 0.740, Sb= 0.800,

Ac=0.130, Bd= 0.590, Ve= 1.380 a, b, c, d, e(C.West,G. Guenegou, Y. Zhang, L- Morin-Allory,

Insights into chiral recognition mechanisms in supercritical fluid chromatography. II. Factors

contributing to enantiomer separation on tris-(3, 5-dimethylphenylcarbonate) of amylose and

cellulose stationary phases. J. chromatography A 1218(2011) 2018-2057.

Table 3.21. Predicted solute descriptors for methamphetamine Descriptors E S A B L V Values 0.830 0.296 1.570 1.008 3.619 1.380

The values in bold are the calculated solute descriptors. The overall standard deviation

for the predicted solute descriptors for methamphetamine is 0.090 log unit. The A and B

descriptors will depend on the process coefficients a and b and also on the interaction between

78

the solute and the stationary phase. All coefficients reflect differences in the properties of two

phases between which the solute are being transferred. By observing the structure of

methamphetamine (Figure 3.5), there is only one hydrogens that can form hydrogen bond, but

the A descriptors is a little bit high with A= 1.570. The hydrogen bond interaction is highly

dependent on the specific atoms present and on the orientation of the molecule involved in the

interaction. This occurs when a hydrogen atom is covalently bonded to an electronegativity

element such as nitrogen, oxygen, fluorine and at the same time interacting with the lone

electrons on the nearby electronegativity element( or in some case with the π system of aromatic

rings). Also one can expect a higher solute descriptor value of A (hydrogen bond acidic) when

one of the other four solute descriptors (E, S, B, L) is very low. The drug also shows some basic

tendency because of the amine group; with the B descriptor equal 1.008. The nitrogen with the

lone pair also makes the drug a little polar with the S value of 0.296. The A descriptor

characterizes solute hydrogen bond donating ability. If neither phase can donate hydrogen bonds

then the coefficient B will be zero. The Ostwald descriptor L is a combination of solute

properties, one being a general measure of solute size and the second being the ability of a solute

to interact with a solvent phase through dispersion forces. The S descriptor has dipolarity and

polarizability effect within it, so does the L parameter, thus it’s difficult to separate or to

distinguish the exact distribution of polarity, dispersion and induction effects in the coefficient of

these parameters [57, 58]. Methamphetamine improves concentration, energy and alertness while

decreasing appetite and fatigue.

79

Figure 3.5. Structure of methamphetamine

3.2.3.4 Heroin

Calculating log of retention time is determined through equation19 to equation 25(Table

3.9.7)

Table 3.22. Observed and calculated retention data for heroin Stationary phase Experimental LogtR Calculated LogtR ZB wax plus --- --- ZB 35 1.345 1.387 TR1MS 1.278 1.124 TR5 1.280 1.248 TG5MS 1.294 1.244 TG1301MS 1.320 1.486 Octanol/water 1.580 1.586

The literature solute descriptors for heroin are E= 1.530, S= 2.21, A = 0.00, B = 1.92, V

=2.6598

Table 3.23. Predicted solute descriptors for heroin Descriptors E S A B L V Values 1.937 2.224 0.000 2.136 7.021 2.660

The calculated solute descriptors are in bold. The overall standard deviation for the

predicted solutes descriptors for heroin is 0.106 log unit. The structure of heroin (Figure 3.6)

shows that there are no acidic hydrogen, therefore heroin exhibits no acidic characteristic. The A

descriptor is zero, meaning there is no hydrogen bond ability in heroin. The heroin shows some

basicity due to the nitrogen element with the B descriptor value of 2.136. The S descriptor has

dipolarity and polarizability within it, thus the S descriptor value is 2.224. Nitrogen and oxygen

do contribute to the polarizability and dipolarity of heroin. It’s very difficult to discern the exact

80

distribution of polarity, dispersion and induce effects in the coefficient of those parameters as

mentioned for the methamphetamine [57-58]. The size of L does increase as the solutes increase.

Heroin is highly addictive drug derived from morphine which is obtained from opium poppy

plant.

Figure 3.6. Structure of heroin (left) and morphine(right)

3.2.3.5 Ketamine

Calculating log of retention time is determined through equation19 to equation 25(Table

3.9.9)

Table 3.24. Observed and calculated retention data for ketamine Stationary phase Experimental LogtR Calculated LogtR ZB wax plus 1.249 1.264 ZB 35 1.189 1.203 TR1MS 1.153 1.079 TR5 1.152 1.147 TG5MS 1.164 1.154 TG1301MS 1.174 1.226 Octanol/water 2.900 2.903

The solute descriptors for ketamine are Ea= 1.280, Sb= 1.420, Ac =0.130, Bd =0.890, Ve=

1.832. a, b, c, d,e(C.West,G. Guenegou, Y. Zhang, L- Morin-Allory, Insights into chiral recognition

mechanisms in supercritical fluid chromatography. II. Factors contributing to enantiomer

separation on tris-(3, 5-dimethylphenylcarbonate) of amylose and cellulose stationary phases. J.

chromatography A 1218(2011) 2018-2057.

81

Table 3.25. Predicted solute descriptors for Ketamine Descriptors E S A B L V Values 1.393 1.004 0.000 1.125 6.640 1.832

The calculated solute descriptors values are in bold. The overall standard deviation for

the predicted solutes descriptors for ketamine is 0.041 log unit. Although the calculated

descriptor A shows no ability of hydrogen bond, A is zero; it’s obvious that ketamine has some

hydrogen bond ability by looking at its structure. There is one hydrogen donor in ketamine

structure. The molecule shows some tendency of being basic with the nitrogen element. The

chlorine, nitrogen and oxygen element emphasize the polarity effect on ketamine; thus the S

descriptor is 1.004. One can expect a high value on the polarity descriptor, but as mentioned

early on, the S and L descriptors both have dipolarity and polarizability include in their

parameter which makes it harder to know the exact distribution of polarity, dispersion and induce

effects in the coefficient of these parameters. The dipole –dipole interaction depend on the

orientation of the molecule. Ketamine is considered a dissociative anesthetic, which means the

drug distorts the users’ perception of sight and sound, and produces feelings of detachment from

the environment.

Figure 3.7. Structure of ketamine

Table 3.26Summary of predicted solute descriptors for nicotine, oxycodone, methamphetamine, heroin and ketamine

Drugs E S A B L V Nicotine 0.865 0.870 0.000 1.073 5.469 1.371 Oxycodone 2.015 2.563 0.286 1.706 5.471 2.264 Methamphetamine 0.830 0.296 1.570 1.008 3.619 1.380

82

Heroin 1.937 2.224 0.000 2.136 7.021 2.660 Ketamine 1.393 1.004 0.000 1.125 6.640 1.832

3.3 Conclusion

The Abraham solvation model is a good approach to predict drugs properties. The

Abraham solvation model parameter can be used to characterize the gas chromatography

stationary phase by providing some important chemical information about the stationary phase.

The Abraham solvation model predicts fairly accurate molecular descriptors. It’s important to

know the drugs properties in order for one to model or study a new drugs. Once the drugs

properties are known from the solute descriptors, we can predict on how drug will interact with

different phase or different system. Then one can understand how the drugs will interact with

some biological barrier. The cost of putting the drugs to the market is very high, by using the

Abraham model solvation equation; one can reduce the time and money that needed to be spent.

The instrument use to acquire the retention time is the gas chromatograph with the flame

ionization detector. Mathematical correlations between the logarithm of retention time of illicit

drugs and the solute descriptors from the Abraham model can be established. Linear free energy

relationship (LFER) of Abraham model predicts retention behavior of most compounds and

drugs by comparing the experimental logarithm of retention data with the calculated logarithm of

retention data. Not all drugs did run on all six columns used in this experiment. Some drugs

have higher boiling point that exceed the maximum temperature of the gas chromatography

column. Some drugs are not volatile enough and can’t be run on GC. The b basicity process

coefficient is not very suitable to found or calculated with the gas chromatography due to the

lack of stationary phase with strong hydrogen bonding ability. In order to improve the accuracy

of the prediction, it’s necessary to have more data point for the drugs. More stationary phase can

also be added to improve the prediction. The HPLC (high pressure liquid chromatography) can

83

also be used to study drugs because of the GC limitation of temperature. This experiment shows

that all linear free energy relationship parameters of solutes may be determined using gas

chromatography or experimental techniques. The solvation model can help facilitate the

prediction of further system properties for compounds lacking experimental values. The

molecular solute descriptors obtained from this experiment have many chemical, biological and

pharmaceutical important properties. The molecular solute descriptors can be used to predict skin

permeability, whether or not the drug can cross the brain blood barrier. The obtained molecular

solute descriptors for the illicit drugs studied in this experiment are important to determine why

such drug can cross the brain easily compared to the other drugs based on the acidity, basicity or

polarity of the drug. The process coefficients are the average value over the range of

temperatures. In this study, we were able to determine the solute descriptors for the illicit drugs

experimentally, not by using software or any computational method.

84

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[41] Laura M. Sprunger Grubbs., Characterization of Novel solvent and Absorbents for chemical separation, May 2011

[42] J.M.Santiuste, J.A. Garcia-Dominguez, Study of the retention interactions of solute and stationary phase in the light of solvation model theory, Analytica Chimica Acta, 2000, 335-346.

[43] William E. Acree, Jr., Laura M. Grubbs and Michael H. Abraham (2011). Selection of Ionic Liquid Solvents for Chemical Separations Based on the Abraham Model, Ionic Liquids: Applications and Perspectives, Prof.Alexander Kokorin (Ed.), ISBN: 978-953-307-248-7

[44] H. M. McNair, J. M. Miller, Basic Gas Chromatography, 1998.

[45] Dr. Aslihan Kerc, GAS CHROMATOGRAPHY, Enve 202 power point presentation.

[46] Dr. Thomas G. Chasteen Split/splitless and on-column gas chromatography injectors notes from Sam Houston State University. http://www.shsu.edu/~chm_tgc/GC/GCinject.html

[47] Agilent J & W GC Column Selection Guide

[48] John V. Hinshaw., The flame Ionization Detector, LCGC North America vol. 23, issue 12 Dec, 2005

[49] Abraham, M. H.; Zissimos, A. M.; and Acree, W. E. Jr., Partition of solutes into wet and dry ethers; an LFER analysis, New J. Chem., 2003 , 27, 1041- 1044.

[50] Abraham, M. H.; Acree, W. E. Jr., The Correlation and Prediction of Butane/Water and Gas/Butane Partition Coefficients, Can. J. Chem., 2005 , 83, 362-365.

[51] Abraham, M. H.; Zhao, Y. H., Characterisation of the water/o-nitrophenyl octyl ether system in terms of the partition of nonelectrolytes and of ions, Phys. Chem. Chem. Phys., 2005 , 7, 2418-2422.

[52] Abraham, M. H.; Martins, F., Human skin permeation and partition: General linear free-energy relationship analyses, J. Pharm. Sci., 2004, 93, 1508-1523.

[53] Sprunger, B.H. Blake-Taylor, A. Wairegi, W.E. Acree Jr., M.H. Abraham, Journal of Chromatography A 1160 (2007) 235-245.

[54] Abraham. H.; Poole, F. Colin; Poole K. Salwa; Classification of stationary phases and other materials by gas chromatography, Journal of Chromatography A, 842(1999) 79-114

[55] T.O. Kollie, C.F Poole, J. chromatogr. 550(1991) 213.

[56] Stovall, D. M.; Givens, C.; Keown, S.; Hoover, K. R.; Rodriguez, E.; Acree, W. E. Jr.; Abraham, M. H., Solubility of crystalline nonelectrolyte solutes in organic solvents: Mathematical correlation of ibuprofen solubilities with the Abraham solvation parameter model, Phys. Chem. Liq., 2005 ,43, 261-268.

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[57] M. Vitha, P. W. Carr, The chemical interpretation and practice of linear solvation energy relationships in chromatography, Journal of Chromatography A, 2006, 1126, 143–194.

[58] Abraham, M. H.; Adam Ibrahim, Andreas M. Zissimos, Determination of sets of solute descriptors from chromatographic measurements, Journal of chromatography A, 1037(2004) 29-47.

[59] A.T. James, A.J.P. Martin, Biochem. J. 50 (1952) 679.

[60] A.J.P. Martin, R.L.M. Synge, Biochem. J. 35 (1941) 1358

[61] L. M. S. Grubbs, Characterization of Novel Solvents and Absorbents for Chemical Separations May 2011.

[62] Timothy W. Stephens, Matthew Loera, Amanda N. Quay, Vicky Chou, Connie Shen, Anastasia Wilson, William E. Acree, Jr. and Michael H Abraham, Correlation of solute transfer into toluene and ethylbenzene from water and from gas phase based on the Abraham Model, The open Thermodynamics Journal, 2011,5,104-121